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  • 1
    Electronic Resource
    Electronic Resource
    Noninteger principal quantum numbers increase the efficiency of Slater-type basis sets (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 1-11 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Roothaan-Hartree-Fock (RHF) calculations are carried out for the ground states of the atoms from helium to xenon using a minimal basis set of Slater-type functions whose principal quantum numbers are allowed to take variationally optimal noninteger values. The resulting energies are substantially superior to those obtained previously under the usual restriction that principal quantum numbers be positive integers. The energy lowering relative to the single-zeta wave functions of Clementi and co-workers ranges from 0.0066 Eh in He to 11.2 Eh in Xe. Our results are superior to those obtained by Höjer using a minimal basis set of unconventional binomially screened basis functions. Noninteger principal quantum numbers benefit d-orbitals the most; physically realistic negative d-orbital energies are obtained in all cases including those transition-metal atoms for which a conventional single-zeta STF basis leads to positive d-orbital energies. © 1997 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Ab initio study on the reaction of Sc+ + CH4 → Sc+(SINGLE BOND)CH2 + H2 (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 23-27 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio study on the reaction of the ground state (3D) and the excited state (1D) of Sc+ with methane was performed. Reaction channels on the singlet and triplet potential surface (PES) and the reaction mechanism are examined and discussed. Three regions of the potential surface was studied: the molecular complex, the C(SINGLE BOND)H insertion products, and the transition states for the reaction. Comparisons between singlet and triplet PESs show that the excited state (1D) of Sc+ has more reactivity with methane than does the ground state (3D) due to the spin quantum number conservation with the more stable insertion intermediate. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of hybridization displacement charge on the description of electrostatic potentials of molecules with multiple electrophilic sites (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 67-76 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The importance of the hybridization displacement charge (HDC) in describing molecular electrostatic potential (MEP) maps was demonstrated by studying six molecules; pyrazine N-oxide, para-nitropyridine, 5-nitropyrimidine, 3-nitropyridazine, N2, and N2O. It is shown that continuously distributed HDC-corrected Löwdin charges reproduce the MEP features of these molecules, most of which have competing electrophilic sites, in agreement with ab initio results. Further, it is found that for homonuclear diatomic molecules MEP minima can be located properly using HDC-corrected Löwdin (or HDC-corrected Mulliken) continuously distributed charges, but these features cannot be obtained using the conventional Löwdin (or Mulliken) charges. It was shown that the order of molecular electric field (MEF) values near the different electrophilic sites becomes changed when one moves away from the molecules. Thus, pyridine-type nitrogen atoms are the preferred binding sites close to the molecules, while at large distances, effects of oxygen atoms of the NO groups become dominant. © 1997 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Crystalline and local vibrations of paired bases in poly(dG)-poly(dC) interacting with the h-b-1 hydrogen bond (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 115-124 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some types of atomic vibrations in a chain of the DNA type constructed of G-C pairs were studied. These are the atomic vibrations of the lateral groups of guanine and N(3)H(1)H(2) of cytosine connected by the hydrogen bond h-b-1 and the vibrations of the centers of masses of bases in the direction parallel to bonds h-b-i, i = 1-3. The vibrations mix partially due to the dependence of the energy of the bond h-b-1 on its length and split into two bands because of the interaction between neighboring base pairs. It was shown that the excitation of the bond h-b-1 results in the splitting off of the two local vibrations and in a small deformation of the chain in the vicinity of the pair with the localized hydrogen bond. The law of the dispersion of band vibrations, values of the split-off frequencies, and degree of poly(dG)-poly(dC) chain deformation were determined. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of screened nuclear attraction and electron repulsion molecular integrals over Gaussian basis functions (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 273-278 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analytical solutions to the Yukawa-like screened Coulomb nuclear attraction and electron repulsion molecular basic integrals, as well as to the basic integrals required to compute the virial coefficient, over Gaussian basis functions, are derived and cast into a practical closed form, suitable to interface with modern codes for the calculation of molecular electronic structure. © 1997 John Wiley & Sons, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Photoelectron spectra of molecules. II. Carboxylic acids and their esters (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 303-314 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: He I photoelectron (PE) spectra of four carboxylic acids and five esters are measured. Semiempirical and ab initio quantum chemical calculations are used for the interpretation of the spectra. The complex approach which uses empirically established relationships (the dependence of valence electron ionization energies on proton affinities in the gas phase, on the core level ionization energies, and on the structure) was developed. © 1997 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular orbital analysis of chemical carcinogens (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 323-328 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simple molecular orbital calculations are employed in searching electronic parameters which may characterize the chemical carcinogens. Using frontier orbitals, the carcinogen-DNA bond formation is described as an electron transfer from the highest occupied molecular orbital (HOMO) of DNA to the lowest unoccupied molecular orbital (LUMO) of the carcinogen. Analysis of the DNA bases units shows that the electron donation occurs preferentially at the guanine site. The calculated low LUMO energy of several carcinogens indicate correctly the electrophilic character of these compounds. The difference between the carcinogen and the ultimate carcinogen is analyzed. Epoxides, free radicals, alkylating agents, and other metabolite forms are studied. A reasonable correlation is found between the LUMO energy and the carcinogenic function. © 1997 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Generalized relativistic effective core potential: Gaussian expansions of potentials and pseudospinors for atoms Hg through Rn (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1107-1122 
    Details
    ISSN: 0020-7608
    Keywords: relativistic pseudopotentials ; heavy atoms ; method of molecular calculation ; electronic structure ; Gaussian approximation ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Gaussian expansions of the generalized relativistic effective core potential (GRECP) components are reported for elements Hg through Rn. The accuracy of the analytical GRECPs is estimated by calculations of atomic transition energies with the numerical one-configurational wave functions in comparison with Dirac-Fock calculations. The results of the corresponding calculations with the RECPs of other groups are also given. An “averaged error” in the reproduction of the transition energies without the change of the occupation number of the 5d-shell is an order of magnitude smaller than that for the RECPs of other groups. As is demonstrated for the transitions with the change of the occupation number of the 5d-shell in mercury, the largest absolute error of the GRECP is only 1.5-2 times smaller than that of the energy-adjusted pseudopotential (PP) or the RECP of Ross et al. with the same space of explicitly treated electrons. However, the dispersion of these errors is 19⋅10-4 au for the energy-adjusted PP, 35⋅10-4 au for the RECP of Ross et al. and only 4⋅10-4 au for the GRECP. One-configurational spin-averaged calculations of the molecular properties for HgH and HgH+ are carried out and compared with the corresponding results of Häussermann et al.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1107-1122, 1997
    Additional Material: 17 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of the free surface of liquid formamide (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1123-1131 
    Details
    ISSN: 0020-7608
    Keywords: MD simulations ; liquid surface ; formamide ; molecular orientation ; molecular surface density ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular dynamics simulations of liquid formamide(HCONH2) were carried out using the GROMOS software. The formamide molecule is represented by all of its atoms with all internal degrees of freedom. In contrast to other simulations dealing with bulk properties, this study focuses on the interface liquid-vacuum for the first time. We show that the molecular plane is tilted out of the surface, exposing the HCO group to the vacuum.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1123-1131, 1997
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical study on Pd dimer and trimer interaction with the hydrogen molecule (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 29-45 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The H2 interaction with the Pd dimer and trimer were studied using multiconfigurational self-consistent field (MC-SCF) calculations with the relativistic effective core potential (RECP); the correlation energy correction was included in the extended multireference configuration interaction (MRCI), variational and perturbative to second order. Here, we considered the Pd2 first six states: 3Σ+u, 1Σ+g, 3Πg, 3Δxy, 1Σ+u, and 3Σ+g. For them, the four geometrical approaches included were the side-on H2 toward Pd2, for the hydrogen molecule in and out the Pd dimer plane; the perpendicular end-on H2 toward Pd2; and the perpendicular end-on Pd2 to H2. The Pd2 ground state is 3Σ+u, which only captures H2 in the C2v end-on approach, softly relaxing the H(SINGLE BOND)H bond. The closed-shell 1Σ+g captures the H2 molecule in all the approaches considered: The side-on approach of this state presents deep wells and relaxes the H(SINGLE BOND)H bond, and the end-on approach captures H2 with a relatively longer H(SINGLE BOND)H distance and also a deep well. The 3Πg state was the only one which did not capture H2. For the triangular Pd3 clusters, H2 was approached in the C2v symmetry in and out of the Pd3 plane. In the triangular case, H2 was absorbed in both spin states, with deep wells and relaxing the H(SINGLE BOND)H distance. The linear Pd3 singlet and triplet states capture outside of the Pd3 and break the H(SINGLE BOND)H bond. © 1997 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Total and partial decay widths in vibrational predissociation of the HeI2 van der Waals complex for lower initial vibrational excitations (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 89-96 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We presented a calculation of the total and partial decay widths of vibrational predissociation (VP) of the HeI2 molecule for low initial vibrational excitations from the lowest van der Waals (vdW) state with total angular momentum J = 0. A time-dependent golden rule wave-packet method was employed in our numerical calculations for the decay widths. The computed total decay widths, lifetimes, and rates of VP are in fairly good agreement with those extrapolated from the experimental data available. Predicted total decay widths as a function of initial vibrational levels exhibit a highly nonlinear behavior. These results demonstrate that a quantum mechanical decay mode for low vibrational excitation remains as well. The total propagation time needed in the time-dependent golden rule wave-packet calculations is much shorter than is the lifetime of the predissociation of HeI2. It is shown that the final-state interaction between the fragments is important for determining the final rotational-state distribution (partial decay width). We find that the major peak position in the final rotational-state distribution shifts to lower rotational energy levels with increase of the initial vibrational quantum number, which is evidently different from that for higher vibrational levels. This fact can be clearly explained by the dependence of the amount of kinetic energy released to the product degrees of freedom on the initial vibrational state. © 1997 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    A very accurate grid method for the solution of Schrödinger equations: The helium ground state (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1065-1078 
    Details
    ISSN: 0020-7608
    Keywords: very precise eigenvalues ; very accurate grid method ; general solution for Schrödinger equations ; rapidly convergent treatment for helium eigenvalues ; superconvergence ; optimization of grids ; treatment of continuum ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extension to the theory of Schrödinger equations has been made which enables the derivation of eigenvalues from a consideration of a very small part of geometric space. The concomitant unwanted continuum effects have been removed. The theory enables very convergent or “superconvergent” calculations. In the case of the helium ground state, E=-2.90372437703411987 Eh was obtained from 251 terms. The result is comparable to that from the largest variation calculations so far carried out reinforced by extrapolation techniques. The theory is extensible to atoms and molecules irrespectively of the number of electrons or nuclear centers. In these cases, the advantage of “superconvergent” calculations will be more pronounced than in the case of helium.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1065-1078, 1997
    Additional Material: 9 Tab.
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  • 13
    Electronic Resource
    Electronic Resource
    Resonances and antibound states in a Morse potential (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 239-244 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We calculate the resonant and antibound state energies for a Morse potential with a centrifugal barrier using Siegert boundary conditions. Starting with a complex wave number k (purely imaginary for bound and antibound states), we integrate numerically from the origin up to a matching point using Numerov's method. The inward integration is performed using the corresponding (first-order) Riccati equation. The complex eigenvalues are found by matching the two logarithmic derivatives. We find narrow shape resonances within the well, above the dissociation limit, and broad resonances above the centrifugal barrier. Antibound states are found even with J = 0. © 1997 John Wiley & Sons, Inc.
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  • 14
    Electronic Resource
    Electronic Resource
    On the dynamics of a linear and a nonlinear quantum oscillator with randomly changing harmonic frequency (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 265-272 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerical experiments with a nonlinear (λχ4) oscillator which has its harmonic frequency changing randomly with time reveal certain interesting features of its dynamics of quantum evolution. When λ = 0, the level populations are seen to oscillate. But, as the nonlinear coupling is switched on (λ 〉 0), a threshold is reached at λ = λc when the evolution is seen to be characterized by an abrupt transition dominantly to the highest available state of the unperturbed (initial) oscillator. It is shown that this transition probability is maximized at a particular value of λ. The time threshold for this transition decreases with increasing nonlinear coupling strength. The numerically obtained structures of the underlying quantum-phase spaces of the linear and nonlinear random oscillators are examined. Possible use of these results in a problem of chemical origin is explored. © 1997 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Electronic structure of testosterone: A semiempirical and ab initio assessment (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 279-289 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Testosterone (17β-hydroxy-4-androsten-3-one) was studied by the semiempirical AM1 and PM3 and ab initio STO-3G*, 3-21G*, and 6-31G* methods. The goals were to compare those methods and to know the electronic structure of the hormone. Full geometry optimization was performed, and two crystal conformers (T1 and T2), and experimental dipole moment in solution were used for comparison. One conformer with a dipole moment similar to the solvated conditions was generated. Total energy, entalphies, dipole moments, charges, electrostatic potentials, and highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbital (LUMO) were calculated. Root-mean-square (RMS) index of the theoretical molecules against T1 and T2 showed best results with the 3-21G* and 6-31G* methods, while AM1 gave better energies than PM3. Dipole moments were directed toward the OH group and the botton face of the A ring. The frontier orbitals were located along the C4-C5 π bond, particularly the LUMO was split between C4 and C5, predicting the action of enzymes at C5 yielding to 5α and 5β-reduced androgens. Electrostatic potentials might be also of biological importance since they are coincidental with the dipole-moment orientation. Finally, it is interesting that the solvatedlike conformer, its properties, and the OH group laid between the same group of T1 and T2 and with a total energy between the crystals and the gas phase or in vacuo conditions. This results might also explain the biology of testosterone and use them to model the hormone-receptor interaction. © 1997 John Wiley & Sons, Inc.
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  • 16
    Electronic Resource
    Electronic Resource
    A study of methanetetraol dehydration to carbonic acid (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 315-322 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two alternative dehydration reactions C(OH)4 → (HO)2CO + H2O and C(OH)4 + H2O → (HO)2CO + 2H2O are studied by ab initio Becke3LYP/6-311 + G** and MP2/6-31G** methods. Calculated energy and geometry characteristics of intermediates and transition states predict a catalytic effect of one water molecule and the exothermism of the transformations. Relevant HF/6-311 + G**, HF/6-31G**, HF/6-31G, and HF/3-21G calculations were performed for comparison. © 1997 John Wiley & Sons, Inc.
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  • 17
    Electronic Resource
    Electronic Resource
    Hydrogen-bonding effects, electrostatic potential, and the antitumor activity of flavone acetic acid and related compounds. III. Ab initio studies on the conformation space (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 97-113 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Restricted geometry optimizations at the ab initio SCF level with the 3-21G basis set were employed to investigate the conformation space of flavone acetic acid (FAA) and its related compounds. All the conformations are produced from a conformation which is, according to our previous work, probably the active conformation in terms of antitumor activity shown by these compounds. Detailed studies on FAA were carried out while only brief discussions are made on the analogs. The main results obtained are that (1) FAA is a very flexible molecule, e.g., with the energy barrier up to about 3 kcal mol-1 from the reference conformation, the important torsional angle τ1 can change from 27.0° to 117.0°, τ2 from -168.0° to 2.0°, and τ3 from -50.0° to 30.0°; (2) the hydrogen-bonding effect plays an important role in determining lower-energy conformations; (3) among all the FAA conformations considered, some are active and some are inactive; (4) it seems that the analogs will have similar behavior to FAA when the torsional angle τ3 is restricted to the values which are around the equilibrium values; and (5) the hypothesis put forward previously has been further developed in this work. Now, we postulate that efficient charge transfers will lower the energy and that proper charge transfers will activate the molecule. There are mainly two different types of charge transfer corresponding to two different types of conformation, which are specified in this article. © 1997 John Wiley & Sons, Inc.
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  • 18
    Electronic Resource
    Electronic Resource
    Modeling properties of the HF dimer in argon clusters (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 55-65 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We compare geometry configurations, vibrational properties, and electronic structures of (HF)2 in a free state and inside argon atom shells Arn. For the first stage, molecular dynamics calculations for the (HF)2 · Ar62 heterocluster are performed with the help of model potentials HF(SINGLE BOND)HF, Ar(SINGLE BOND)Ar, and Ar(SINGLE BOND)HF. Then, ab initio quantum chemistry analysis is carried out for the smaller systems (HF)2 · Ar15 and (HF)2 · Ar6 when keeping the argon atoms closest to the trapped dimer. We conclude that the hydrogen-bonded complex (HF)2 gains some extra stability inside the argon shells, originating primarily from a decrease of intermolecular distance RFF. Electronic structure calculations are in accord with the changes in dynamical properties, namely, a noticeable increase in the vibrational frequency assigned to the F(SINGLE BOND)F stretching mode (+25 cm-1) and decrease in rms deviations for the corresponding coordinate δFF. In addition to these changes, the argon atoms of the nearest solvent shell donate a small fraction of electron charge which is spent for an increase of population of the antibonding orbital σ*Hf(SINGLE BOND)Ff of the free monomer unit and shift orbital energies primarily of the lone-pair fluorine species. These shifts are greater than the changes due to geometry alterations and the possible inaccuracies of the calculation scheme. © 1997 John Wiley & Sons, Inc.
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  • 19
    Electronic Resource
    Electronic Resource
    Numerical solution for the ground-state energy of the anisotropic Heisenberg model (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 13-21 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the anisotropic Heisenberg model is carried out by solving the Bethe ansatz solution of the model numerically as a function of the anisotropy parameter for finite N. A brief introduction to the limit of the infinite chain is presented. The energy for a few special limiting cases of the anisotropy parameter in the Hamiltonian are worked out. Numerical results for finite cycles as well as for the infinite chain are given. Comparison can then be made with the case of finite increasing N. © 1997 John Wiley & Sons, Inc.
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  • 20
    Electronic Resource
    Electronic Resource
    Evaluation of a characteristic atomic radius by an ab initio method (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 47-53 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The MELD program is employed to evaluate the Slater average potential v(r) felt by an electron at the point r within an atom. The characteristic radius R of the atom is then defined by the classical turning point equation v(R) = -I, where I denotes the first ionization potential of the atom. The atomic radii defined in this way have a close correlation with the van der Waals atomic radii. © 1997 John Wiley & Sons, Inc.
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  • 21
    Electronic Resource
    Electronic Resource
    Accurate nonrelativistic energies for 2Pe states of the Li isoelectronic series (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 77-88 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly accurate upper bounds for several 2Pe states of the Li isoelectronic series obtained by extensive Hylleraas-Cl calculations are given. The best value for the 22Pe state (1s2p2) of Li is -5.21373920 au. The evaluation of the occurring integrals is given explicitly. Additionally, we present some expectation values and isotope energies of the Li isoelectronic series. © 1997 John Wiley & Sons, Inc.
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    Efficient evaluation of the algebrants of VB wave functions using the successive expansion method. I. Spin S = 0, ½ (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 245-259 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient expansion method for the evaluation of VB matrix elements is introduced. The overlaps of VB wave functions of N electrons can be treated as algebrants, i.e., generalized determinants, of N × N matrices. An algebrant can be expanded with subalgebrants of lower orders in a successive way. By choosing Rumer spin bases and appropriately arranging the expansion, it is found that the number of unique subalgebrants involved in the expansion increases in a quite moderate way with N. In contrast to the traditional symmetric group approach, which explicitly utilizes all N! representation matrices, the new strategy incorporates the group theoretical factors in a simple way in the successive expansion. As only the unique subalgebrants are further expanded, the computational effort required by the new strategy scales in a very acceptable manner with the increasing number of electrons. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62: 245-259, 1997
    Additional Material: 5 Tab.
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  • 23
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    Electronic Resource
    Characters of two-row representations of the symmetric group (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 261-264 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Characters of irreducible representations (irreps) of the symmetric group corresponding to the two-row Young diagrams, i.e., describing transformation properties of N-electron eigenfunctions of the total spin operators, have been expressed as explicit functions of the number of electrons N and of the total spin quantum number S. The formulas are useful in various areas of theory of many-electron systems, particularly in designing algorithms for evaluation of spectral density moments. © 1997 John Wiley & Sons, Inc.
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  • 24
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    Computation of bond dissociation energy for sulfides and disulfides with ab initio and density functional theory methods (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 291-296 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The geometries and S-H, S-S, and S-C bond dissociation energies for hydrogen sulfide, hydrogen disulfide, methanethiol, dimethyl disulfide, and dimethyl disulfide were calculated with both ab initio (ROHF and MP2), hybrid (BHandH, BHandHLYP, Becke3LYP and Becke3P86), and nonlocal (BLYP and BP86) density functional theory (DFT) methods. In all studies the 6-31 + G(d) basis set is used. The computed results are compared to the experimentally obtained values, targeting the selection of a suitable ab initio or DFT method for the study of these systems. © 1997 John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
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  • 25
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    Theoretical study on the pyrolysis mechanism and kinetics of β-hydroxyketones (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 297-302 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism and kinetics for the decomposition of β-hydroxypropaldehyde, primary and secondary β-hydroxyketones, were studied by using ab initio RHF/6-31G and RHF/6-31G* methods. The activation barriers of these reactions were refined to be 39.57, 40.10, and 36.80 kcal mol-1 at the MP2/ /RHF/6-31G* level, respectively. The calculated results show that each decomposition is a concerted process with hydrogen transferring and bond breaking via a six-membered cyclic transition state. The thermal rate constants of the decomposition of primary and secondary β-hydroxyketones were obtained by calculating microcanonical probability fluxes through each transition state. It is theoretically confirmed that methyl substitution at the hydroxyl carbon of β-hydroxyketones causes a small enhancement in rates. The theoretical investigations of the mechanism and the rate constants are in agreement with the experimental results. © 1997 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 26
    Electronic Resource
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    Power series with rational coefficients for two-electron atom energies (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1079-1089 
    Details
    ISSN: 0020-7608
    Keywords: large-order perturbation theory ; lie algebra ; three-body problem ; symbolic computations ; helium atom ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of o(4, 2) operator replacements is generalized. As a result, the series whose limiting values when the variable goes to  +∞ should correspond to the two-electron atom energies now have rational coefficients. This generalization allows one also to compute the series for the case of singlet S symmetry, a case which could not be considered in the previous original formulation of the method. Series with rational coefficients for the helium singlet and triplet S ground-state energy are calculated up to order 41 and 45, respectively. Moreover, symbolic computations also allow one to give the first few coefficients of these series for arbitrary values of the nuclear charge Z. Finally, a new method for analytic continuation to the limit  +∞ is presented for the energies of the helium singlet and triplet ground states.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1079-1089, 1997
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  • 27
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    A study of bond-cleavage and bond-formation processes in some simple metathesis reactions (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1099-1106 
    Details
    ISSN: 0020-7608
    Keywords: metathesis reactions ; bond order ; free valence ; minimum energy path ; nonsynchronization ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A few simple atom-transfer reactions (i.e., Ȧ+X-A→A-X+Ȧ) are studied by quantum mechanical ab initio methods. Emphasis is given to the detailed analysis of density matrices rather than to the energetics. Results reveal that during these reactions a small free valence always develops on the migrating atom at the transition state. The barriers in these reactions arise from the greater extent of bond cleavage in the reactant than that of bond formation in the transition state. Analysis of bond orders estimated from bond lengths using Pauling's relation also leads to the fact that the bond-cleavage process is more advanced than is the bond-formation process in these reactions.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1099-1106, 1997
    Additional Material: 4 Ill.
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  • 28
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    The multireference constant denominator perturbation theory for one-particle systems and its application to the anharmonic oscillator (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 15-34 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper a multireference constant denominator perturbation theory (CDPT) is developed to reduce incomplete basis set errors arising when solving the Schrödinger equation with a finite basis set. The advantage of this method is that very few basis functions are needed, and all calculations if carried out to high enough order in the perturbation treatment effectively use a complete basis set. As a first step the theory has been restricted to one-particle Hamiltonians and applied to the anharmonic oscillator to study the convergence properties. For perturbation calculations carried out to fifth order, results from Pade approximates show an improvement in accuracy of between one and three orders of magnitude.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560370103
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  • 29
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    Coherence in disordered condensed matter. III: H+ and OH- ionic conductance and proton transfer reactions in aqueous solutions (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 155-165 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The physical context of the high ionic conductivity of the H+ and OH- ions in aqueous solutions is considered. Quantum dynamical aspects of the mobility of these ions are investigated, especially within the framework of the complex scaling method (CSM). It is argued that the high ionic mobilities under consideration are due to quantum delocalization of the ions as well as mass interference of the H+ ions with water protons. This effect is formally described with the aid of the coherent-dissipative structures, which become spontaneously created in the solution owing to the thermal motion. In particular, (1) a novel connection between the proton transfer rate (as measured by NMR) and the mobilities of the considered ions (as determined by conductivity measurements) is derived. Additionally, (2) a relation connecting the activation energies of the above reaction rates with the ionic mobilities is found. The above relations contain no fitting parameters. Comparisons with experimental results is made, which also reveals the predictive power of the present CSM treatment in the field of microdynamical processes in condensed phases.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560370206
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    Announcement (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 207-207 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370210
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  • 31
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    A tensor representation of the real spherical functions for the continuous group O3+ in cartesian coordinates: Example of eulerian rotations (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 655-662 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this article is to give a practical way for the use of real spherical functions in another frame than the frame in which they have been defined. For instance, we calculate physical properties from a local frame and use them in the general frame, deduced one from the other by Eulerian rotations on the coordinates. The power of the method is in the use of cartesian coordinates and in the definition of a scalar product between these functions to set up the complete vectorial space generated by these representations of the group O3+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370504
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  • 32
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    Quantum processes in semiconductors, 2nd ed. by B. K. Ridley (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 309-310 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370309
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    Robert G. Parr (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 313-313 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370403
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  • 34
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    The Hubbard connection (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 389-402 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hubbard theory is an approximation to the Pariser-Parr-Pople theory which presents many of its important features in a relatively simple form. Our Hubbard Hamiltonian employs a single electron-correlation parameter: 0 ≤ x ≡ U/(t + U) ≤ 1, where t is the one-electron hopping integral (the negative of the Hueckel β), and U is the Hubbard one-center, two-electron repulsion parameter. This parameter provides the Hubbard connection between the following: (1)Molecular orbital and valence bond theory(2)The exchange approximation and full CI(3)Conductors and insulators(4)Fermi-Dirac and Boltzmann statistics(5)Normal and superconductorsWe present Hubbard theory in the freeon (spin-free) formulation where each N-electron state is pictorially represented by a Gel'fand diagram which specifies both the orbital configuration and the multiplicity. The simplicity of the freeon formulation makes the Hubbard connection quite transparent.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560370410
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    On the difference in bond orders between HMO and PPP methods (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 437-448 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have examined variations in bond orders in conjugated hydrocarbons that follow improvement in MO calculations on going from topological Hückel MO to self-consistent Pariser-Parr-Pople-type calculations. Differences in individual bond orders can be interpreted as pointing to increased weights of selected Kekulé valence structures. Significantly, so indicated valence structures are those with the largest number of formal Kekulé benzene rings or the largest contribution to molecular resonance energy in terms of conjugated circuits.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370414
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    The PPP-CI scheme as a fundamental physical model (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 497-508 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Parametrized computational procedures and simplified physical models of molecular reality are often related to one another but are by no means the same thing. With special reference to work by Koutecky and by Cizek, Paldus et al., it is shown here that the PPP model rests on a simple but physically sound electrostatic picture of a molecular π system, and its intrinsic difference from an independent particle model is emphasized. As an illustration of the heuristic power which makes physical models powerful tools of theoretical research, ground state charge transfer GSCT, in situ molecular electronegativity, and the principle of electronegativity equalization are derived within the PPP-CI scheme, no use being made of molecular orbitals, and the assumptions on which the CT theory rests are made explicit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370418
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    Quantum-chemical investigation of Buckminsterfullerene and related carbon clusters (I): The electronic structure and UV spectra of Buckminsterfullerene, and other C60 cagesWith great admiration and respect for the contributions that Drs. Pariser, Parr, and Pople have made throughout their careers and in particular for helping to organize our thoughts on molecular electronic spectra and for supplying quantum chemistry with its most beloved model Hamiltonian. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 599-607 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic structure of C60 cages are examined by use of the INDO and INDO/CI methods. The calculated spectrum of Buckminsterfullerene has one allowed low-lying band at 27,300 cm-1, to be compared with an experimental value of 25,900 cm-1. These calculations suggest that other cage structures are not stable, or they are not ground state singlets.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560370426
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    The use of localized molecular orbitals and the polarization propagator to identify transmission mechanisms in nuclear spin-spin couplings (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 663-677 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extension of the IPPP (inner projections of the polarization propagator) method to theoretically analyze transmission mechanisms of indirect nuclear spin-spin couplings is presented. The localization technique used is modified so that all the canonical molecular orbitals of a compound may be localized to represent chemical bonds, lone pairs, and the corresponding antibonding molecular orbitals. These localized molecular orbitals, together with the polarization propagator, are used to obtain an intuitive picture of how a coupling is generated as a sum of terms, each one consisting of two particle-hole single excitations. This picture can be used to identify underlying transmission mechanisms and quantitatively evaluate their importance toward the total coupling. The paramagnetic spin-orbit and the spin-dipole interactions are studied in detail.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370505
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    Computational models for proton transfer in biological systems (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 701-711 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational scheme based on a “mixed basis set” approach is applied to the study of the structure and the energetics in proton transfer systems. Five hydrogen-bonded systems of the type (CH3HnA ‥ H ‥ BHmCH3)+, where A and B can be N, O, or S, have been investigated with various minimal and extended basis sets. Calculations with the extended basis set yield double-well potential energy curves, which the minimal basis set is unable to reproduce. Calculations with the mixed basis set, constructed from an extended basis set on the atoms engaged in the hydrogen transfer part and a minimal basis set on the rest of the molecule, give predictions of geometries, potential energy curves, and relative energies similar to the results from the extended basis set. Inclusion of polarization functions in the mixed basis set becomes essential in systems that contain third row atoms. This scheme should become useful in studies of large molecules in which different parts can be represented at different levels of computational complexity.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560370508
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  • 40
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    How to find a saddle point (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 773-783 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper explains a method for finding saddle points on a multidimensional surface and shows how it may be used to define saddle-point seeking curves that have properties similar to well-known orthogonal trajectories. It is shown that a gradient extremal is a special case of one of these curves, and its chemical significance as the path, defined by local criteria, which starts from a stable structure and leads to a transition state, is discussed briefly in relation to the intrinsic reaction coordinate. It is emphasized that this theory gives a natural method for locating points that have Hessians of similar structure to those of transition states.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370606
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    Roothaan's open shell theory from the viewpoint of an orthogonal group (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 753-771 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Explicit equations for the constants a and b of the energy as the average expectation value for the minimal domain of states giving the Roothaan energy functional are derived in terms of the total spin value and the “seniority” quantum number. The state with off-diagonal long-range order can appear in the framework of the Roothaan scheme for the quasidegenerate system as an alternative to the Hund rule. Admissible many-electron states are established for all configurations of the icosahedral symmetry group systems, and corresponding a and b coefficients are calculated.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370605
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  • 42
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    The correlation potential for two-electron atomic ions (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 811-819 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The correlation potential is computed for two electron atomic ions with atomic numbers from 1 to 10 using the charge density reconstructed from a natural orbital expansion of a Kinoshita-like atomic wave function. Over the wide range of densities involved, the correlation potentials are not even approximately a local function of the density.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370609
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    The symmetrized basis function method for SU(2) and its application to the total spin states of many-electron systems (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 41-53 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper, the symmetrized basis function method is extended and used for the classification of the total spin states of many-electron systems. The reduction matrix, which is expressed as a series of products and direct products of matrices is derived. It is very advantageous that the method can be completed by computer. As an example, the reduction matrix for a 5-electron system calculated by IBM PC computer and the classification of the total spin states is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380105
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    The TST-CEQ calculations on the heavy-light-heavy Cl + HCl reaction (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 75-83 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper, the TST-CEQ calculated results including the reactive cross sections and rate constants for the Cl + HCl reaction at the specified vibrational state of the HCl are presented. It is shown that the oscillatory behavior of the system in the three-dimensional world does not appear, and the larger the vibrational quantum number of HCl, the smaller the cross sections ¯QTST-CEQ (E, ν) are at a given total energy used in the calculations, but the larger the reactive rate, constants KTST-CEQ (T, ν) are at a given temperature. The KTST-CEQ (T, v) is the same as when first published, and the average reactive rate constants KTST-CEQ (T) are close to the ones by Garrett and Schatz et al.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560380107
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    Masthead (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380301
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  • 46
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    Optimization of molecular electronic structure calculations. 1. Local symmetry and local symmetricized orbitals (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 383-388 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A formalism is suggested of the so-called local symmetricized orbitals to be used for the construction of a symmetricized basis in molecular electronic structure calculations. The local symmetricized orbitals are defined as additive contributions to the symmetry orbitals of a molecule that arise from symmetry operations of a corresponding atom. The local symmetricized orbitals are transformed according to the irreducible representations of the molecular symmetry group. This approach appears to be most suitable for the optimization of quantum mechanical calculations accounting for the spatial symmetry of compounds under consideration. This fact is due to the formalism of the local symmetricized orbitals that explicitly accounts for the local symmetry of basis function centers, which is essential for such optimization.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380302
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    Spectroscopic studies on the protonation of Schiff bases (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 173-179 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This short review concerns the protonation of Schiff bases by halogenic or carboxylic acids with a bias toward the chromophore of visual and bacterial rhodopsins. It is pointed out that the weak acids available in these pigments could not protonate the retinyl Schiff base 100% and that a supporting mechanism is needed to achieve full protonation. Our Fourier transform infrared studies both at room and low temperatures relating to this problem are summarized, and the propable role of water is emphasized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380212
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    Localization of virtual orbitals (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 215-219 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the MBPT in the localized representation requires that both the occupied and the virtual orbitals obtained by the canonical HF equation should be localized. The localization of the occupied orbitals is straightforward in general by any localization method. It is shown that by using Boys' method the localized virtual orbitals are spatially well separated and transferable not only in minimal basis sets.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380216
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    MNDO CI study of the photoisomerization about polar double bonds (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 231-238 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cis-trans photoisomerization of ethylene, some of its methyl and fluoro derivatives, methaniminium, and aminoborane was studied and twisted biradical geometries of these molecules in So, S1, and S2 states were optimized using the half-electron version of the MNDO method with configuration interaction. The results are quite satisfactory, in good agreement with available ab initio data.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380219
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    Ground-state multiplicity by spin-extended Hartree-Fock method (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 279-282 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New possibilities of the spin-extended Hartree-Fock method in determining the sequence of energy levels are analyzed and demonstrated by the example of some oxygen-contained compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380223
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    Density matrix of crystalline systems. I. Long-range behavior and related computational problems (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 395-417 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The one-electron density matrix (DM) of crystalline systems is discussed, especially concerning its longrange behavior; reference is made throughout to systems treated at a Hartree-Fock-LCAO-SCF level of approximation. The analysis is performed on the assumption of generally smooth behavior of eigenvalues and eigenvectors in k (reciprocal) space, so that they can be expressed by means of a truncated Fourier expansion. This assumption allows us to obtain analytic approximations for the DM, on the basis of the information collected at a few, suitably selected sampling k points. It is therefore possible at the same time to discuss the influence of structural parameters (dimensionality of the system, existence and shape of the Fermi surface, structure of the chemical bonds) and to set up a computational scheme that is general and simple enough.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380304
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    Sur une tentative d'unification des théaories quantiques de la cancèrisation par les polyacènes: I. Thèorie des règions M, L, et B (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 461-486 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study is a unified approach to quantum theories of polyacen carcinogenesis. Part I discusses the M, L, and B regions theory. Although the M region of polyacens is much less reactive than is the K region, the chemical reactivity of these two regions parallels each other. Consequently, the K-L Pullman's theory may be reformulated by replacing the K region by the M region. The M-L regions theory improves all the quantum structure-carcinogenic activity relationships obtained previously in the K-L framework. Moreover, it would appear that in these correlations, the most important role is played by nonconcerted electrophilic reactions. We suggest that the M-L modified Pullman's theory and the Bay (B) region theory, proposed by Jerina et al., are related to different steps of the metabolic activation mechanism leading to ultimate carcinogen: the first step for the Pullman's theory and the carbocation step for the theory of the Bay region. We have termed the “M, L and B regions theory” as this unified approach to the problem of polyacens carcinogenesis.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380308
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    Masthead (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380401
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    Physical quantification of the biological effectiveness of ionizing radiations (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 501-520 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role, and limitations, of the fundamental physical quantities used in our current system of dosimetry for the protection of individuals against the hazardous effects of ionizing radiation is discussed briefly. A major limitation is the inability to correlate biological data, in a unified way, as a function of linear energy transfer with the consequent necessity for quality factors.From consideration of the various interaction processes undergone by charged particles in the equilibrium slowing down spectra generated by the incident radiation field, it is shown that good correlation of biological effects, for all radiation types, can be achieved in terms of linear primary ionization. The implication is that delta-ray effects play at most a very minor role, at moderate fluences, and that, consequently, the absorbed dose is an unsuitable parameter for describing radiation effects. Structure in the radiosensitive targets is observed to have a critical dimension of about 2 nm. It occurs only when double-stranded DNA is present and the magnitude of the inactivation probability is consistent with double-stranded breaks being the significant lesion. Calculation is made of the yield of lesions as a function of the mean free path for primary ionization.Differential spectra of radiation quality are obtained for monoenergetic electrons (0.2 keV to 30 MeV); for characteristic X-rays from carbon, aluminium, neon, potassium, copper, silver, and tungsten; for 50 kV X-rays, 250 kV X-rays, 241Am, 137Cs, and 60Co gamma rays; and for neutrons with energies between 0.1 and 50 MeV. Damage by electrons is shown to be predominant at the ends of their tracks between 50 and 200 eV, whereas this is not so for the proton recoil spectrum generated by neutrons above 1 MeV.Proposals are made for a unified system of dosimetry that is independent of radiation type and that obviates the need for quality factors. The method is thought to be of general applicability to irradiations by nuclides incorporated into mammalian cells, by ingested emitters, and by external sources.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560380402
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    A population analysis based on hybrid orbitals (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 597-605 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By a way of partitioning of Mulliken overlap populations, the hybrid orbitals of central atoms and ligands are obtained by the CNDO method. The dipole moments of some hybrids are calculated using the hybrid orbitals obtained, and they are mostly in accordance with experimental values. In addition, overlap integrals may be decomposed into components, and then σ, π, and δ hybrid orbitals can be obtained.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380409
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    Preface (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 611-611 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380502
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    Transition structures and energy barriers of pericyclic reactions in the CASSCF approach (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 653-664 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five energy hypersurfaces of the most examined pericyclic reactions have been investigated by using ab initio SCF, CASSCF, and the semiempirical AM1 methods. The systems are H4, H6, C3H6, C4H4, and C3OH4. Stationary points and their sets of harmonic vibrational frequencies have been calculated by means of analytical gradient techniques in the frameworks of the respective approaches. ZPE corrected energy barriers are based on single-point calculations including dynamical correlation corrections by CAS-CI(SD)+DC, CASCEPA, or MP2.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560380507
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    Masthead (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560381701
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    Structural and electronic analysis of peripheral benzodiazepine ligands: Description of the pharmacophoric elements for their receptors (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 1-25 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to understand the interaction mode of benzodiazepine ligands with their peripheral binding sites, the structural and electronic properties of a benzodiazepine Ro 5-4864, Alpidem, PK 11195, and some analogs are characterized at the ab initio molecular orbital level. Conformational and electronic data, with a particular emphasis on electrostatic aspects, i.e., molecular electrostatic potentials, Mulliken atomic charges, and potential-derived charges, are used as input within molecular superimpositions to elaborate the pharmacophoric elements for the peripheral benzodiazepine ligands. A putative three-dimensional (3-D) steric and electronic model is proposed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560381705
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    The integrated molecular transform as a correlation parameter (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 27-34 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular transform is an alternate means of considering numerical representations of molecules in a manner designed to generate indices that can be related to structural and physiochemical parameters. The literature has shown that the transform, actually the Fourier transform, is operable on representations such as Cartesian coordinates or graphically derived depictious reflected by adjacency or distance matrices. The resulting curve may be used to give a binary index of the molecule or integrated to give an area-related index; either of these indices may be used as a correlation parameter in structure-activity studies. In this instance the individual bond distance matrices of a series of structurally diverse compounds served as input for a transform program. The derived index was then used to correlate both physical property and pharmacological activity indices for the series; correlation coefficients were comparable to those reported for the valence molecular connectivity parameter of Kier and Hall. The study also showed that lower correlation coefficients resulted when the index was based on the transform of hydrogen-suppressed structures.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560381706
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    Strategies for walking on potential energy surfaces using local quadratic approximations (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 263-276 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An algorithm for locating stationary points corresponding to local minima and transition states on potential energy surfaces is further analyzed. This method utilizes local gradient and Hessian (i.e., first and second energy derivative) information to generate a series of “steps” that are followed to the desired stationary point. By designing the step sequence to move energetically downhill in all coordinates, local minima can be found. By stepping uphill along one local eigenmode of the Hessian while minimizing the energy along all other modes, one locates transition states. Key elements of this development are more efficient parameterization of the step vector in terms of quantities that permit the direction (i.e., uphill or downhill), and length of the step to be carefully controlled, and implementation of the ability to explore “side channels” as attractive options occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382427
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    Photoelectron spectroscopy of biologically active molecules. 21. ThiooxamidesPart 20. para-Quinones, Semiquinones and Aromatic Ketones, Int. J. Quantum Chem. Quantum Chem. Symp. 24, 799 (1990). (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 813-820 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The HeI photoelectron (PE) spectra of No,No-dimethyl-monothiooxamide (1,) its analogue Ns,Ns-dimethylmonothiooxamide (2), dithiooxamide (3), N,N′-dimethyldithiooxamide (4), and N,N,N′,N′-tetramethyldithiooxamide (5) are presented. The results of CNDO/2 calculations, the PE spectra of the related compounds acetamide, thioacetamide, thiourea, and their methyl derivatives, and HeI/HeII intensity considerations are used to assign the spectra.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560382479
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    Geometry optimization of molecules within an LCGTO local-density functional approach (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 851-857 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe our implementation of geometry optimization techniques within the linear combination of Gaussian-type orbitals (LCGTO) approach to local-density functional theory. The algorithm for geometry optimization is based on the evaluation of the gradient of the total energy with respect to internal coordinates within the local-density functional scheme. We present optimization results for a range of small molecules which serve as test cases for our approach.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382483
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    How to become famous by being wrong in scienceThis paper is a written version of the after-dinner talk given on march 21, 1990 at the banquet of the 30th anniversary of the sanibel symposia. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 881-889 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382486
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    Call for contributions to paper symposium on computational methods in quantum chemistry, solid-state theory, and molecular biology. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 893-893 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382487
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    Perturbation theory of intermolecular interactions: What is the problem, are there solutions? (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 531-547 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We review the nature of the problem in the framework of Rayleigh-Schrödinger perturbation theory (the polarization approximation) considering explicitly two examples: the interaction of two hydrogen atoms and the interaction of Li with H. We show, in agreement with the work of Claverie and of Morgan and Simon, that the LiH problem is dramatically different from the H2 problem. In particular, the physical states of LiH are higher in energy than an infinite number of discrete, unphysical states and they are buried in a continuum of unbound, unphysical states, which starts well below the lowest physical state. Claverie has shown that the perturbation expansion, under these circumstances, is likely to converge to an unphysical state of lower energy than the physical ground state, if it converges at all. We review, also, the application of two classes of exchange perturbation theory to LiH and larger systems. We show that the spectra of three Eisenschitz-London (EL) class, exchange perturbation theories have no continuum of unphysical states overlaying the physical states and no discrete, unphysical states below the lowest physical state. In contrast, the spectra of two Hirschfelder-Silbey class theories differ hardly at all from that found with the polarization approximation. Not one of the EL class of perturbation theories, however, eliminates all of the discrete unphysical states. The best one establishes a one-to-one correspondence between the lowest energy states of the unperturbed and perturbed Hamiltonians, and a one-to-two correspondence for the higher states. We suggest that the EL class perturbation theories would be good starting points for the development of more effective perturbation theories for intermolecular interactions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382452
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    Electron propagator test of atomic natural orbital basis sets (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 585-591 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron propagator calculations of Sc and Ti ionization energies employing contractions based on atomic natural orbitals reveal the soundness of this approach for choosing basis sets. Errors in total energies greatly exceed those for ionization energies, where contraction errors are reduced to less than 1 mhartree. Systematic improvements involve retention of natural orbitals with lower occupation numbers and augmentation with diffuse and polarization functions.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382457
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    Dynamics and neural network computation (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 633-644 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Computation is carried out by the motion of the state of a dynamical system. This description unites digital and “neural network” computation. The use of an energy function to understand and to program batch mode computation on feedback networks is reviewed. Recognizing words in continuous speech illustrates the use of a compound network to solve a real-world problem where data arrive continuously over time. A new tool, a Lagrangian formulation, is introduced for studying networks which oscillate, and as a means for formulating problems which need to optimize functional integrals.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560382461
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    Exchange and correlation in density-functional theory and quasiparticle theory (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 681-682 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382466
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    Coupling of electrons and lattice wave packets in superconducting metastable states formed at high pressure (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 717-719 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382471
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    Multicenter spherical gaussian expansion of molecular orbital wavefunctions (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 701-706 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Floating spherical Gaussian basis sets are systematically expanded for a series of small molecules: methane, ammonia, ethane, and acetylene. Localized (nonorthogonal) molecular orbitals are each constructed as a linear combination of up to five functions of the form exp [- (r - R)2/ρ2], where the size ρ and the position R of each function is optimized according to the variation principle. Basis sets are obtained for the C and N cores, the C —; H and N — H bonds, the N lone pair, and the C — C and C—C bonds. Only three to five fully optimized functions are required to describe the main features of each bond orbital, including the negative lobes in the wavefunctions at the heavy atoms and the local maximum in the electron density at the hydrogen atoms. The energies obtained with three basis functions for the core orbitals are intermediate between the results of RHF-SCF calculations with STO-3G and 3-21G basis sets.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382469
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    Interaction energies of diatomic molecules using partial antisymmetry and Hartree-Fock atomic wave functions (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 753-765 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We provide a numerical test of a new approach to calculating approximate interatomic interaction energies based on partial antisymmetry (PA) [Adams, Chem. Phys. Lett. 68, 511 (1979)]. We use spin-coupled products of single determinant atomic wave functions to approximate a particular primitive wave function of the diatomic. Three methods are used: (1) the conventional full antisymmetry (FA) approach, in which the primitive wave function is antisymmetrized and the difference of expectation values of the total energies of the diatomic and atomic systems is calculated, (2) the PA approach, in which only some of the terms of the antisymmetrizer are applied to the primitive wave function, and the energy expressions are simplified based on approximations to the PA theorem [Adams, op. cit.], and (3) a hybrid approach based on a combination of assumptions from the first two approaches, which is comparable to the work of Dacre and McWeeny [Proc. Roy. Soc. London A317, 435 (1970)]. Results are compared with accurate potential curves from the literature. Interaction energies were calculated for the X 1Σ+g states of Ne2, Li2, and Na2, the X 1Σ+ states of LiNa and LiF, the x 3Σ+u states of Li2 and Na2, x 7Σ+u, and x 3Σ+ LiNa at several internuclear distances. In all cases but Ne2, the PA and FA interaction energies are much closer to each other than is either to the accurate reference values. In these cases there is thus no significant penalty exacted for the use of PA over FA, even though it is easier to use. By conventional reasoning, neither the PA nor the Dacre-McWeeny approaches should work at short range or for binding molecules, because they truncate expansions of the antisymmetrizer in the energy expression. Our results provide counter examples to change that expectation, thus providing additional evidence in support of an approximate approach based on the PA theorem.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382474
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    Equilibrium and nonequilibrium solvation and solute electronic structure (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 821-833 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When a molecular solute is immersed in a polar and polarizable solvent, the electronic wave function of the solute system is altered compared to its vacuum value; the solute electronic structure is thus solvent-dependent. Further, the wave function will be altered depending upon whether the polarization of the solvent is or is not in equilibrium with the solute charge distribution. More precisely, while the solvent electronic polarization should be in equilibrium with the solute electronic wave function, the much more sluggish solvent orientational polarization need not be. We call this last situation “non-equilibrium solvation.” We outline a nonlinear Schrödinger equation approach to these issues. The nonlinearity arises from the self-consistent aspect that the solute electronic Hamiltonian depends on the solvent electronic polarization which is induced by the solute charge distribution. We illustrate the predictions of the theory for electron transfer reactions, ionic dissociations, and solvation dynamics in polar solvents. Special features of interest include activation barriers that differ markedly from standard predictions, and novel solvent dynamical features.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382480
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    Theoretically-derived, energy-based criteria for aromaticity (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 843-850 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Previous energy-based criteria for aromaticity developed from one electron eigenvalues (using methods ranging from Huckel to ab initio calculations) have not correlated well with experimentally derived criteria such as χ⊥nlcl or chemical reactivity data, and are particularly poor for heteroaromatic compounds. Previous work has shown that criteria derived from the lowest π molecular orbitals of heteroaromatic compounds correlate well with χ⊥nlcl and chemical reactivity, prompting us to modify Kollmar's procedure for determining aromatic stabilization energies by localizing the lowest π orbital rather than the entire π bonding manifold. This modified procedure was implemented with both the natural (NLMO) and Boys orbital localization methods, and was applied to a set of ten five-membered ring heteroaromatics and to pyridine and its diazine derivatives. The new criterion ΔπL correlated well with χ⊥nlcl (R2 = 0.86 (NLMO); R2 = 0.92 (Boys)) for five-membered rings, and with theoretical measures of aromaticity for both sets of heteroaromatics. The Boys procedure gave better overall correlations and was markedly superior for pyrazole and pyridazine.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560382482
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    Biographical information (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 115-117 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380205
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    Triplet-singlet splitting of the alkali metal clusters: Example of the Li6 clusters (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 149-161 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of the geometry on the specifics of the electronic structure of Li6 clusters is studied in detail, since planar and three-dimensional lithium hexamers are found to be of comparable stability. The ab initio CI investigation of the Li6 isomers yields almost degenerate lowest singlet and triplet states for certain cluster geometries. Simple criteria for the energy gap between the lowest triplet and singlet state are derived, and their applicability is demonstrated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380210
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    QCT study of isotopic effects in H + HBr abstraction and exchange reactions (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 321-327 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of quasi-classical trajectories on an LEPS hypersurface was used for studying the influence of the exchange of one or both of the hydrogen atoms for deuterium in the reaction H1 + H2Br. As expected, the reaction cross sections of the exchange and abstraction reactions were found to increase if H1 was replaced by D and decrease if H2 was replaced by deuterium. A similar change in the reaction cross sections have also been observed for vibrationally excited reactants. The distribution of vibrational (rotational) energy is related to the ωe (Be) values of the respective reactants and products.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380227
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  • 78
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    Theoretical study of the reaction Ne + H+2 → NEH+ + H in the 2A′ ground state (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 339-350 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A three-dimensional potential energy surface for the 2A′ ground state of the system (Ne—H2)+ (2Σ+ in collinear geometry) has been calculated at SCF and CEPA levels. This surface describes the abstraction reaction \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Ne} + {\rm H}^ + _2 \to {\rm NeH}^{\rm + } + {\rm H}, $$\end{document} which is endoergic by 0.57 eV (ΔH00) and has been studied recently by different experimental groups at low collision energies. Our CEPA calculations yield an endoergicity of 0.55 eV (ΔH00). The 2A′ surface has a minimum at collinear geometry with RNe - H = 2.29 a0 and RH—H = 2.08 a0 and a well depth of 0.49 eV relative to Ne + H+2. The effects of electron correlation on the shape of the surface and on the well depth are discussed.An analytic fit of the collinear part of the surface has been constructed based on Simon's proposal of using polynomials in the coordinates (R—Re)/R instead of (R—Re). The fitted potential is used for quantum mechanical scattering calculations with the finite element method (FEM). Preliminary results for reaction probabilities for H+2 in different vibrationally excited states are given and compared to the experimental results.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380229
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    Optimization of molecular electronic structure calculations. 2. Calculation of symmetry-reduced matrix elements (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 389-394 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A suggested formalism of the local symmetricized orbitals in conjunction with the selection technique for independent blocks of integrals in an original basis is used for a construction of multielectron Hamiltonian matrix elements in the symmetry orbital basis. The optimal molecular electronic structure calculation algorithm with the Hartree-Fock-Roothaan method in the symmetricized basis was obtained as a result. The minimal number of fundamentally distinguished (symmetry attributed) elements both in original and in symmetricized basis is used in the calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380303
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  • 80
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    Ab initio calculations of the structure and properties of molecules. By C.E. Dykstra, Elsevier Science Publishers, B.V., 1988 (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 205-205 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370209
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    Masthead (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370301
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  • 82
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    Differentiability of degenerate electronic wave functions with respect to parametric variables (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 249-256 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The present paper is aimed at differentiability of electronic wave functions, with respect to parametric variables, in the presence of electronic degeneracy. An analysis is made of a wave function, constructed so that it has the largest domain of parameter space in which it is differentiable, with the help of Berry's formula for the geometric phase. In particular, the electronic wave functions, in presence of a double degeneracy in two- and three-dimensional parameter spaces, are studied in detail. It was found that the three-parameter-dependent wave function is differentiable everywhere except along an axis starting from the degenerate point where it is discontinuous. The two-parameter-dependent wave function is differentiable everywhere except at the degenerate point where it is disocontinuous. These singularities are expected to have consequences on wave functions having parametric variables as arguments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370305
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  • 83
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    A comparative analysis of the electrostatic potentials of some structural analogues of 2,3,7,8-tetrachlorodibenzo-p-dioxin and of related aromatic systems (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 271-289 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have carried out an ab initio STO-5G computational analysis of the electrostatic potentials of four structural analogues of the highly toxic 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and four related aromatic systems benzo[a]pyrene, benz[a]anthracene, and two isomeric benzoflavones. These systems, to varying degrees, induce aryl hydrocarbon hydroxylase activity and are believed to interact with the same cytosolic receptor in initiating their biochemical responses. Our present results for the TCDD analogues support and have allowed us to further qualify our early observations regarding factors which are linked to high biological activities in the dibenzo-p-dioxins and structurally similar systems. We find that a high degree of activity appears to require nonoverlapping negative potentials above all or most of the lateral regions, with an observed optimum range of magnitudes. In systems with central oxygens, it is required that the negative oxygen potentials be small and weak; however, oxygen negative regions in the molecule are not necessary for high activity. The observed differences between the potential patterns of the four aromatic systems and those of TCDD and its active analogues may reflect an inherent dissimilarity in the nature of their interactions with the cytosolic receptor. That the carbonyl oxygen negative potential of 7,8-benzoflavone is significantly more negative than its isomer's supports earlier speculation concerning the former's more effective inhibiting effects on metabolic oxidation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370307
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    N-band Hubbard models for copper oxides and isoelectronic systems. New models for organic and organometallic magnetic conductors and superconductors (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 167-196 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic structures of undoped and doped copper oxides and other related oxides are investigated on the basis of the N-band Hubbard models. The Hubbard Hamiltonians for clusters of transition metal oxides are exactly diagonalized by the full valence-bond (VB) configuration interaction (CI) method in order to elucidate populations of doped holes, electronic excitation energies, etc. Possible mechanisms of the high-Tc superconductivity for oxide superconductors are discussed on the basis of the calculated results, together with available experiments. The analysis of correlation and spin correlation effects on doped copper oxides indicates theoretical possibilities of new models for organic and organometallic magnetic conductors and superconductors. Organic and organometallic analogs to copper oxides are therefore proposed on the basis of these results.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370207
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    Theoretical study of transitions involving three rydberg series in two-valence electron systems: MgI and its electronic sequence (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 221-240 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oscillator strengths for transitions involving levels of three spectral series, 3s2 1S → 3snp1P0, 3s3p 1P0 → 3snd 1D, and 3s3p 1P0 → 3sns 1S, have been computed and analyzed for several ions of the MgI isoelectronic sequence (MgI-TiXI). The quantum defect orbital (QDO) formalism has been used throughout, and the results are comparable to those of more complex theoretical procedures.
    Additional Material: 15 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370303
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    Electronic Resource
    Masthead (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370601
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  • 87
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    Upper and lower bounds to the Schrödinger equation eigenvalues (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 747-752 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is presented for obtaining rapidly convergent upper and lower bounds to the eigenvalues of the Schrödinger equation for one-dimensional and central-field models. The logarithmic derivative of the wave function is written as a Padé approximant and the bounds are obtained by simply counting the real zeroes of the denominator.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370604
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  • 88
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    Introduction (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 317-317 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370405
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  • 89
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    The origin of PPP theory (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 349-371 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An historical account is given of the part played by the author in the development of PPP theory in the early 1950s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370408
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    On the connection between semiempirical molecular orbital theories and effective hamiltonians: A constrained variational point of view (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 415-422 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The idea of interpreting the semiempirical MO theories from a constrained variational point of view is explored. A density-based approach is developed for calibrating the parameters of useful semiempirical Hamiltonians of molecular electronic structure theory. Results of some numerical experiments with model Hamiltonians of constrained variational origin are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370412
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  • 91
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    Vibronic spectral behavior of molecules. XIII. Theoretical contribution to the vibronic coupling and the dushinsky effect on the S1 ← S0 absorption and the S1 → S0, S2 → S1, and S2 → S0 fluorescences of azulene (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 25-39 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Based on the completely optimized S0, S1, and S2 molecular geometries of azulene, the vibronic structure of the S1 ← S0 absorption as well as of the S1 → S0, S2 → S1, and S2 → S0 fluorescences is investigated theoretically within the adiabatic approximation. By means of theory-experiment comparisons, the influence of non-Condon terms and of the Dushinsky effect on the vibronic structure of azulene spectral behavior is discussed. Typical for the S1 ← S0 absorption and the S1 → S0 fluorescence are vibronic transition moment contributions of Condon type, whereas the interpretation of azulene S2 → S1 and S2 → S0 fluorescences is successful only within the scope of the Herzberg-Teller approach by taking into account vibronic coupling terms and, additionally, the Dushinsky effect in the latter case. An analysis of the relevant vibrational modes is given.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380104
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    Masthead (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380201
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    Publications of Rudolf Zahradník (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 99-114 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380204
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  • 94
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    Solvent effects on mechanism of tetramethylene polymerization (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 129-138 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization mechanism of tetramethylenes was reinvestigated under inclusion of solvent effects. The approach of a methanol molecule to a borderline diradical, a typical diradical, and a typical zwitterion was studied by a valence, charge, and dipole moment analysis of SINDO1 calculations. Whereas the solvent molecule has no effect on the character of the zwitterion, the borderline diradical was found to switch to a zwitterion at the approach of the methanol molecule if the distance between the donor carbon and the methanol oxygen is below 2 Å. A similar switch of character was observed for the typical diradical at CO distances below 1.5 Å. From energy considerations it is concluded that borderline diradicals can follow a zwitterionic polymerization mechanism in polar solvents, whereas typical diradicals are much less likely to do so.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380208
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  • 95
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    Computational chemistry on a PC (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 163-171 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a package of some IBM PC programs that may find application in computer-aided molecular design. PCGEOM constructs and visualizes molecular models from bond lengths, bond angles, and dihedral angles, from Cartesian coordinates, or from stored fragments. It may prepare output files to be used as input for other programs, like CNDOB (conventional CNDO/2) or PCMEP using the bond increment (BI) method for the calculation of molecular electrostatic potentials. PCPROT is in preparation and will use Protein Data Bank coordinates to visualize and manipulate protein molecular models. Starting from these, it will calculate electrostatic potentials using the BI method and/or monopoles adjusted to reproduce ab initio values for amino acid residues. FSCF is based on a CNDO-type approximation and uses strictly localized molecular orbitals in order to partition large molecules into a central fragment, a polarizable region, and a fully transferable environment. The partition allows one to handle relatively large systems with up to 200 atoms. To illustrate applications, we present estimation of relative inhibitory potencies of a series of substituted triazines on chicken liver dihydrofolate reductase.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380211
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  • 96
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    Nonlinear coupling in the quantum statistical theory of proton transfer dynamics (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 209-213 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possible role of the nonlinear coupling on the character of the dynamics of particle transfer process is investigated. The analysis and solutions of the kinetic equation indicate that nonlinear coupling causes symmetry breaking of particle transfer potential and determines possible equilibrium structure of the system. Dissipative coupling characterizes the rate of the system to reach thermodynamic equilibrium and along with nonlinear coupling and parameters of the system determines in a unique way the resulting equilibrium structure of the system.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380215
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  • 97
    Electronic Resource
    Electronic Resource
    Quantum chemical calculations of silicon clusters in silicon dioxide and point defects in β-cristobalite (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 239-244 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A local electronic-state density in β-cristobalite in the empirical tight-binding approximation has been calculated by the recursion method. In particular, silicon clusters have been considered in β-cristobalite containing up to three coordination spheres of silicon atoms.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380220
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  • 98
    Electronic Resource
    Electronic Resource
    Transfer of electronic excitation energy in partially disordered polymer chain (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 297-309 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new form of the generalized master equation for electronic excitation transfer in a partially disordered polymer chain was derived. Within this equation, in order to differentiate the transfer in ordered parts of the partially disordered polymer chain, we decomposed the memory function of electronic excitation into several parts. These parts are memory functions associated with various types of subdynamics of electronic excitation. The partially disordered polymer chain where the disorder is caused by conformational defects is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380225
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  • 99
    Electronic Resource
    Electronic Resource
    The effect of interlayer interactions on chemisorption pattern stability: Hydrogen atoms on graphiteDisclaimer: This work represents the views of the authors and not necessarily the official position of the U.S. Military Academy, the U.S. Army, or any other governmental agency. Work of the U.S. Government, not subject to copyright restrictions. (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 799-817 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Extended Hückel band calculations, frontier crystal orbital analysis, and degenerate-level perturbation theory are used to evaluate the effect inclusion of bulk-layer interactions has on the relative stabilities of ordered overlayers. Five patterns of hydrogen atoms chemisorbed on unreconstructed graphite (11% coverage) are examined for the Bernal (ABABAB…) and registered (AAA…) three-dimensional stackings. The single-layer two-dimensional approximation for graphite is found not to be entirely satisfactory for the type of chemisorption pattern stability questions addressed in this paper.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380604
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  • 100
    Electronic Resource
    Electronic Resource
    Hyperspherical harmonics. Applications in Quantum Theory. By. J. Avery, Kluwer Academic Publishers, Dordrecht, Boston, London, 1989 (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 867-867 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380609
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