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  • 1975-1979  (110)
  • 1976  (110)
  • Computational Chemistry and Molecular Modeling  (110)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976) 
    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
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 381-381 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 383-391 
    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: Another possible application of a previously reported approximation theory for electron repulsion integrals using rigorous error bounds is considered by incorporating the electron density matrix in the approximation scheme. Error bounds are set on the contribution of a given integral to the total energy for a given molecular wave-function; the wave-function is then refined cyclically and additional integrals are computed exactly if necessary until convergence is achieved.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 413-418 
    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 canonical orthornormalisation procedure is derived through an integral equation with a finite rank kernel. Its optimal properties in connection with the problem of approximate linear dependence are established.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 429-437 
    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: First excited singlet and triplet electric dipole polarizabilities are reported. The π polarizability is calculated by means of a modified Rayleigh-Schrödinger perturbation theory and an SCF-LCAO basis. The σ contribution is included by an additive scheme. The polarization of the σ electrons is partially accounted for through an empirical correction. Results compare satisfactorily with a configuration interaction perturbation calculation.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 439-454 
    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 investigated various nonstandard 1s basis functions (generalized Slater-Gaussian, ellipsoidal Gaussian, floating spherical and ellipsoidal Gaussian, rational function, Hulthén approximation, two-Slater-type orbital, generalized Guillemin-Zener function, and various noninteger-n elliptical orbitals) for approximating the 1Σg+ ground state of H2 and He2++. A CI trial wave-function including Σg-type MO's is adopted and molecular integrals are evaluated numerically. The energy improvement on the 1s STO is small except for noninteger-n orbitals which closely approach the “SCF limit”.
    Additional Material: 3 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 473-493 
    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 work involves the derivation of approximate forms for the matrix elements of an ab initio π-electron molecular orbital theory. The result may be described as a complete neglect of differential overlap mathematical formalism plus σ-π exchange. The basis set of π atomic functions for these derivations is a set of approximate Löwdin orthogonalized atomic orbitals (LOAO's) produced by successive pairwise orthogonalization. Using these functions, we derive approximate equations for the one-electron integrals of molecular orbital theory, αμLOAO and βμνLOAO, which, for the first time, show the effects of overlap-coupling in a molecule. Many new methods of approximation enter the theory. There are approximate equations for π-electron, nuclear attraction potentials and for π-electron, σ-core repulsion potentials, all approximations are compared to more accurate calculations where possible. A mechanism is also included for testing the effects of σ-charge shifts upon the results of the π-electron calculations.
    Additional Material: 3 Ill.
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  • 8
    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 developed a many-body version of Woodward-Hoffmann theory which is capable of rapid computation of π-electronic surfaces. This theory, called the Hückel-Hubbard theory, employs Hückel parameters as reaction coordinates and the Hubbard parameter for electron repulsion. We apply it to the cis-trans isomerization of ethylene and to several pericyclic reactions.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 629-642 
    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 simulated ab initio molecular orbital (SAMO) method previously applied to RHF closed-shell and UHF open-shell situations has been applied to open-shell radicals, such as the butyl radical and the pentyl radical, within the RHF open-shell framework. The open-shell Hartree-Fock theory is developed such that a rapidly convergent iterative method for evaluating the SAMO wave-function can be employed. Results closely parallel those for the same systems using the UHF method and are of comparable accuracy to SAMO closed-shell results.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 643-658 
    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 variant of the transcorrelated method of Boys and Handy employing finite differences is presented. It is based upon the following two properties of the transcorrelated Hamiltonian operator C-1HC: (1) C-1HC possesses an energy eigenvalue spectrum which is identical to that associated with H itself; and (2) if \documentclass{article}\pagestyle{empty}\begin{document}$$ C \equiv \begin{array}{*{20}c} \pi & {e^{r_{ij} /2} } \\ {i 〉 j} & {} \\ \end{array} $$\end{document} then C-1HC is free of the singularities of H at the points where the interelectron separation rij is zero. A bivariational principle for approximating the eigenvalues and the left and right eigenfunctions of C-1HC is introduced and the resulting set of coupled integro-differential equations are solved in finite-difference form by means of a coupled self-consistent field, Newton Raphson algorithm. As a preliminary test of the method, a calculation of the ground-state energy of the helium atom is presented.
    Additional Material: 3 Tab.
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 659-668 
    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: Singlet-triplet spin-orbit matrix elements, which govern the lowest 3B1u ← 1Ag transition in typical aromatic molecules like naphtalene and anthracene, are calculated with INDO molecular orbitals and the conventional spin-orbit one-electron hamiltonian. The correct order of magnitude of the triplet radiative lifetimes is obtained for the two molecules, when INDO MO coefficients are referred to a symmetrically orthogonalized basis. The possibility of using the semiempirical Hamiltonian is explored using ab initio wave-functions for a few test cases. Reasonably accurate doublet-doublet and singlet-triplet matrix elements have been computed.
    Additional Material: 6 Tab.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 683-697 
    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 proposed for characterizing pairs of finite dimensional subspaces of the Hilbert space. The method might be helpful for the proper selection of coordinate and projective spaces leading to reliable realizations of the Galerkin-Petrov method for use in quantum chemistry. In order to illustrate the method some numerical results are presented.
    Additional Material: 1 Tab.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 669-681 
    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 an iterative generalization of the minimum principle proposed for electronic systems by Hall, Hyslop, and Rees is investigated. It is shown that this generalization still retains the advantage of using members of a larger class of trial wave-functions, for example those with discontinuities, as initial approximations to the wave-functions. This scheme has the advantage that, at each stage of iteration, an upper bound is obtained which is at least as good as that obtained previously.The theory is first applied to the hydrogen atom. It is then adapted to estimate the Hartree-Fock energy of the helium atom, the Hartree-Fock limit being obtained after a relatively small number of iterations.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 715-715 
    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
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 739-742 
    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 effectiveness of the recently developed method for optimization of one-electron wave-functions is directly examined by means of a simple procedure. By means of the same procedure the dependence of electron correlation on the nuclear charge and on the number of electrons is also investigated.
    Additional Material: 2 Tab.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 743-746 
    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: On the basis of the previously described method for optimization of one-electron wave-functions, a simple procedure has been developed to determine the ionization energies in atomic cases. The procedure gives all the ionization energies at once with relatively high accuracy. This is possible due to optimal distribution of the total electron charge between the individual spin-orbitals.
    Additional Material: 2 Tab.
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 747-760 
    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 general model for the vibrational interactions of the hydrogen bonds in molecular crystals is presented. The energy and the intensity distributions of the IR spectra of the 1-methylthymine and uracil crystals are correctly reproduced.
    Additional Material: 3 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 761-769 
    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 iterative method of solving the Mestechkin spin-extended Hartree-Fock equations is proposed. On this basis projected and spin-extended values of energies and spin densities for some hydrocarbon π-radicals are calculated. Relations among UHF, ASA, AA, projected, and spin-extended energies are discussed.
    Additional Material: 3 Tab.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 781-789 
    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: Introduction of noninteger powers of r (or the elliptical coordinate ξ) in the definition of the 1s AO is shown to give better approximate wave-functions for the ground states of H2 and He2++ than other functions of comparable complexity. This trend is examined for various definitions of hybrid Slater-Gaussian orbitals using a limited CI. The best optimized single-term expansion energy is only 0.000160 a.u. above the “SCF limit” for H2 at R = 1.4 a.u. and 0.000382 a.u. for He2++ at R = 1.3 a.u.
    Additional Material: 5 Tab.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 771-780 
    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: Coupled and uncoupled Hartree-Fock theories are used to compute the electric dipole polarizability of water, ammonia, and methane with three different GTO basis sets. Bounds for the geometric approximation to uncoupled polarizabilities are also computed to examine the accuracy of calculated values. The results are compared with those obtained by a variational-perturbation method proposed by Rebane. The numerical tests provide some information on the correlation terms affecting total computed polarizabilities. The computed values are shown to be in fair or good agreement with experimental data for the largest basis sets. The reliability of Rebane's method with respect to coupled HF procedure is also discussed.
    Additional Material: 4 Tab.
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  • 21
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 791-797 
    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 many-electron theory is developed for the determination of pure spin state wave-functions and energies to avoid the difficulties in doing integration. The Waller-Hartree pure spin state wave-functions are very convenient for this purpose. The required explicit formulas for the values of the Waller-Hartree wave-functions Y(S, M) and HY(S, M) at some physical points are produced, where local orthonormal orbitals are used to simplify the calculation of HY(S, M). A method for the construction of these orbitals is given, and a transformation formula is also given to show the interchangability between the local energy expression and the conventional expectation energy integral.
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  • 22
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 993-1005 
    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 parameters in the Mössbauer spectroscopy, electric field gradient (EFG), and change in the charge density at the nucleus site Δψ2(0) are evaluated on the basis of the CNDO/II method for various compounds of antimony and tin and compared with experimental data. The correlation between the isomer shift adn the quadrupole splitting with these electronic parameters is used to evaluate δR/R and Q and compared with the results of other workers. Different methods for the theoretical interpretation of the Mössbauer parameters are discussed. It was found that Molecular Orbital (MO) methods give quite reliable results for antimony and tin compounds and can be used for elucidating the bonding mechanism in these compounds.
    Additional Material: 4 Ill.
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  • 23
    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: Interrelations between the local and the global aspects of the stability, continuity, and symmetry properties of variational wave-functions are discussed. The spherical limit of one-electron diatomic molecules and the Hartree-Fock approximation of the ground state of the two-electron atom are shown to exhibit the various concepts involved in an ab initio, yet sufficiently simple, manner.
    Additional Material: 7 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 1087-1088 
    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
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  • 25
    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
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  • 26
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 5-20 
    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: Inverses and inverse square roots of overlap matrices are approximated by polynomials constructed on the basis of an integral transform of the metric resolvent and Kublanovskaya's conformal mapping technique. Given reasonable upper and lower bounds for the support of the overlap matrix spectral distribution, the described expansions have significantly better convergence properties than the well known power series methods, yet retain the simplicity of these schemes.
    Additional Material: 3 Tab.
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  • 27
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 21-35 
    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: Extensively optimized Lewis orbital (Frost model) structures are reported for CH3N, CH3NH+, CH3CH, CH3CH2+, CH3BH2, CH2NH, and CH2NH2+ (spiro and planar). Electronic energy differences between these isoelectronic species were estimated by the integral Hellmann-Feynman (iHF) formula, with the hope that satisfaction of the Hellmann-Feynman conditions would lead to accurate iHF values of energy changes. We observed a strongly nonlinear relation between the iHF error and the departure of the overlap of wave-functions of the structures from unity. MO computations in common orbital (not determinantal) basis sets for CH3NH+—CH2NH2+ (planar), CH3N—CH2NH, and CH3CH—CH2CH2 produced greatly improved iHF estimates of energy changes, reducing errors by as much as 80 times. Certain features of the static optimum structures and the transition densities suggested that the syn path for rearrangement of methyl carbene to ethylene is a general feature of rearrangements in these systems.
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  • 28
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    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 10 (1976), S. 37-56 
    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: Inelastic collisions leading to rotationally excited molecular targets and involving protons as projectiles are theoretically examined from the point of view of both the scattering equations in the close coupling formalism and the interaction potentials between the partners.A phenomenological approach is suggested for constructing such interactions and computational results are reported for simple diatomic targets. The inadequacy of more traditional ‘static’ approaches, when called for explaining dynamic couplings with open channels and centrifugal effects, is also discussed.
    Additional Material: 10 Ill.
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  • 29
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    International Journal of Quantum Chemistry 10 (1976), S. 71-86 
    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 relation of the straightforward Rayleigh-Schrödinger perturbation theory for the interaction of two atoms to the asymptotic exchange theory is described. The one-electron case of a hydrogen atom perturbed by a nucleus is examined in detail. It is shown that the asymptotic theory contains an infinite summation of terms in the Rayleigh-Schrödinger series. The nature of the branching between states and its implications for convergence is elucidated.
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  • 30
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    International Journal of Quantum Chemistry 10 (1976), S. 113-121 
    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 various correlation functions, multiplying the monoelectronic space function, is studied and applied to the Helium atom and its isoelectronic series. We used Slater-type basis orbitals and the ground and first excited states have been studied, taking into account the virial and cusp conditions. In the ground state, a very good value for the correlation energy is obtained, using a function of the type \documentclass{article}\pagestyle{empty}\begin{document}$$ 1 - \frac{1}{{1 + 2\alpha }}e^{ - \alpha r_{12} } $$\end{document}For the excited states, this type of function overestimates the assumed value of the correlation energy.
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  • 31
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    International Journal of Quantum Chemistry 10 (1976), S. 187-189 
    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
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  • 32
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    International Journal of Quantum Chemistry 10 (1976), S. 281-297 
    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: Assuming a determinantal form for the wave-functions of free molecules, explicit formula for the first-order interaction energy of many closed-shell molecules has been derived. Provided that the determinants describing the free molecules are constructed from the Hartree-Fock orbitals, the two-, three-, and four-body effects predicted by the first-order perturbation theory are closely related to those which one obtains in the framework of the Löwdin LCAO MO-type approach. The results are illustrated by numerical calculations for the system of three ground-state helium atoms.
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  • 33
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    International Journal of Quantum Chemistry 10 (1976), S. 325-340 
    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 method is proposed for the analysis of components of molecular interaction energy within the Hartree-Fock approximation. The Hartree-Fock molecular orbitals of the isolated molecules are used as the basis for the construction of Fock matrix of the supermolecule. Then certain blocks of this matrix are set to zero subject to specify boundary conditions of the supermolecule molecular orbitals, and the resultant matrix is diagonalized iteratively to obtain the desired energy components. This method can be considered as an extension of our previous method, but has an advantage in the explicit definition of the charge transfer energy, placing it on an equal footing with the exchange and polarization terms. The new method is compared with existing perturbation methods, and is also applied to the energy and electron density decomposition of (H2O)2.
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  • 34
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    International Journal of Quantum Chemistry 10 (1976), S. 307-323 
    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 applied the spin-density-functional (SDF) formalism with the local-spin-density (LSD) approximation to a number of small molecules with the primary aim of testing the approximation for molecular applications. A new numerical method to solve the one-electron wave equation is developed, utilizing the special features of the SDF formalism. We have calculated energy curves, dissociation energies, and equilibrium distances for some diatomic molecules [H2+ (2Σg+, 2Σu+), H2(1Σg+, 3Σu+), He2+ + (1Σg+), and He2(1Σg+)] and the vibrational frequencies of H2. The deviations from the experimental results are typically 1/2 eV for the energies and ≤ 0.1 Å for the distances. We discuss the LSD approximation using the concept of an exchange-correlation hole and make predictions about the applicability to other molecules. The LSD approximation is compared with the Hartree-Fock and multiple-scattering-Xα methods and some difficulties in the latter methods are pointed out. It is argued that the SDF formalism within the LSD approximation has physical advantages compared to the Hartree-Fock and Xα methods and that it should provide a simple and useful method for a broad range of applications.
    Additional Material: 2 Ill.
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  • 35
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    International Journal of Quantum Chemistry 10 (1976), S. 341-358 
    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: It is proposed to calculate electronic structure of atoms and molecules by combining the Thomas-Fermi-Dirac (TFD) theory and a correct quantum mechanical treatment. The potential generated from the TFD treatment of the positively charged cores contains no adjustable parameters and requires no modification for proper asymptotic behavior. To take the exclusion principle into account, the valence electron wave-function is constructed from the n + 1st, n + 2nd, etc. solutions to the one-electron Schrödinger equation using the core potential, where n is the number of core electrons. For the potassium atom, the simple calculations give excellent agreement with experiment for ionization potential, transition frequencies and intensities, magnetic susceptibility, and electric polarizability. From a two-electron configuration interaction wave-function for K-, a value for the electron affinity of K is obtained which agrees with experimental values.
    Additional Material: 6 Tab.
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  • 36
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    International Journal of Quantum Chemistry 10 (1976), S. 379-379 
    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
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  • 37
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    International Journal of Quantum Chemistry 10 (1976) 
    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
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  • 38
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    International Journal of Quantum Chemistry 10 (1976), S. 419-428 
    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 evaluation of interatomic interactions at large separations (R) typically involves neglecting electron exchange, treating the Coulomb interaction between atoms as a perturbation, neglecting third- and higher-order energy contributions, and approximating the Coulomb interaction by a short expansion in spherical harmonics and, usually, powers of R-1. This last approximation, using an approximate perturbing Hamiltonian to evaluate a second-order perturbed energy, is examined here; error bounds and a simple correction are introduced. Three illustrative applications to the H—H+ interaction are given: the error incurred by truncating the spherical-harmonic expansion is bounded, the R-1 expansion is corrected for the overlap of the “atomic” charge distributions, and the R-1 expansion is analyzed to see why it works as well as it does.
    Additional Material: 3 Tab.
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  • 39
    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: Single-exponential Slater type orbitals of the form ψ1 = (1 + L1(r, θ) + L2(r, θ) +…+ Ln(r, θ)) exp (- αr) are examined for their potential use as one-center molecular orbitals. These are then to be used as molecular fragments in a LCMO study. The system examined is HeH+ + with calculated energies and dipole moments being compared to the exact values. These functions behave best in the region of chemical interest (the bonding region) and thus demonstrate a possible usefulness in LCMO calculations and in the field of one-electron diatomics.
    Additional Material: 3 Tab.
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  • 40
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    International Journal of Quantum Chemistry 10 (1976), S. 461-472 
    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 half-projected Hartree-Fock function for singlet states (HPHF) is analysed in terms of natural electronic configurations. For this purpose the HPHF spinless density matrix and its natural orbitals are first deduced.It is found that the HPHF function does not contain any contribution from odd-times excited configurations. It is seen in addition, in the case of the singlet ground states, this function is approximately equivalent to two closed-shell configurations, although the nature of the excited one depends on the nuclear geometry. An example is given in the case of the LiH ground state. Finally, the application of this model for studying systems of more that two atoms is criticized.
    Additional Material: 3 Ill.
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  • 41
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    International Journal of Quantum Chemistry 10 (1976), S. 495-510 
    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 ground-state energy of the beryllium atom is calculated using a variational procedure in which the elements of the two-body reduced density matrix (particle-particle matrix) are the variational parameters. It is shown that, for this problem and with the limited number of spin-orbitals used, the trace condition and the simultaneous nonnegativity conditions on the particle-particle, the particle-hole, and the hole-hole matrices form a complete solution to the N-representability problem.The energy obtained is - 14.61425 a.u., practically identical to the value given by a configuration interaction calculation which uses the same states. The effects of weakening the nonnegativity conditions on each of the matrices in turn were also explored.
    Additional Material: 2 Ill.
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  • 42
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    International Journal of Quantum Chemistry 10 (1976), S. 57-69 
    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 contains a discussion of asymptotic properties of inverses of cyclic overlap matrices relevant to LCAO theory based on localized orbitals. For inverse metric elements, Δlαl′β-1, and for large distances, R, between centres of localized orbital α in cell l and localized orbital β in cell l′, it is shown that: one-dimensional case: \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta _{l\alpha l\prime\beta }^{- 1} \sim{\rm const}{\rm .}\,{\rm exp}\,{\rm (} -{\rm const}{\rm . \times }R{\rm )} $$\end{document} two-dimentional case: \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta _{l\alpha l\prime\beta }^{ - 1} \sim{\rm const}{\rm .}\,\,R^{ - _2^1 } \,{\rm exp}\,{\rm (} - {\rm const}{\rm . \times }R{\rm )} $$\end{document} three-dimentional case: \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta _{l\alpha l\prime\beta }^{ - 1} \sim{\rm const}{\rm .}\,\,R^{ - 1} \,{\rm exp}\,{\rm (} - {\rm const}{\rm . \times }R{\rm )} $$\end{document}These results are quite general and do not presuppose any restrictions as to symmetry (apart from the cyclic one), number of orbitals per unit cell, or vanishing of overlap integrals associated with neighbours beyond a fixed order. By way of illustration, explicit applications to one-, two-, and three-dimensional, simple, mono-orbitalic lattices with first-neighbour overlap only are included.
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  • 43
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    International Journal of Quantum Chemistry 10 (1976), S. 87-111 
    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 algebra of the representation of the special unitary group SU(2), the universal covering of the proper rotation group SO(3), is studied in a nonstandard basis. We are using a basis adapted to a chain of type SU(2) ⊃ … ⊃ G″ ⊃ G′ ⊃ G. The introduction of such a chain enables us to label, at least partially, the elements of the irreducible tensorial sets under SU(2) with irreducible representations of G, G″ G″, …. We are thus led to introduce the restriction SU(2) → … → G″ → G′ → G in the Wigner-Racah algebra of the group SU(2). The physical interest of this machinery lies in the fact that the double group of any point symmetry group belongs, up to an isomorphism, to the considered chain. The formalism described in this paper thus appears to be useful in molecular and solid-state calculations. It is particularly efficient in the fields of vibrational-rotational and electronic spectroscopy of molecules. In Appendix A the master formulae, principally the Wigner-Eckart-Racah theorem, for the Wigner-Racah algebra of a chain of compact topological groups (discrete or continuous) are briefly discussed. Lastly, a programme for computing Clebsch-Gordan coefficients for a chain SU(2) ⊃ … ⊃ G″ ⊃ G′ ⊃ G and numerical results for chains isomorphic to SU(2) ⊃ O′ ⊃ D′4 ⊃ D′2 are described in Appendix B.
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  • 44
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    International Journal of Quantum Chemistry 10 (1976), S. 143-149 
    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 given for generating the Yamanouchi-Kotani genealogical spin eigenfunctions which requires neither storage of eigenfunctions for smaller numbers of electrons, nor summations of large order, nor explicit use of results from the theory of representations of the symmetric group. An explicit formula is given for the coefficients of expansion in terms of spin products.
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  • 45
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    International Journal of Quantum Chemistry 10 (1976), S. 135-141 
    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: Semiorthogonalized orbitals are introduced as a basis of approximate ab initio molecular calculations. The semiorthogonalized orbitals are obtained from the usual overlapping atomic orbitals by means of a generalized Löwdin transformation. The new orbitals are characterized by two features: many overlaps between them are zero, and they are close to their corresponding initial atomic orbitals. On the basis of the semiorthogonalized orbitals, a scheme of integral approximations is proposed which allows one to carry out approximate ab initio calculations with less computational efforts and thus offers a possibility to perform calculations on much bigger molecules with limited computational facilities. Results are presented for model calculations on the anthracene π-electron system. Orbital energies and electron distribution are quite close to the rigorously calculated values.
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  • 46
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    International Journal of Quantum Chemistry 10 (1976), S. 151-162 
    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 space correlation factor is studied in LiH and Li2 molecules, using MCSCF wave-functions. The shape of the Fermi hole is related to the localization of molecular space orbitals, while the Coulomb hole study indicates the importance of symmetry properties of the molecular orbitals involved in excited configurations for the representation of the electronic correlation inside the chemical bond.
    Additional Material: 7 Ill.
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  • 47
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    International Journal of Quantum Chemistry 10 (1976), S. 163-174 
    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 direct method to optimize parameters in nonorthogonal basis orbitals is discussed. The partial derivatives of the energy of the state of interest, not necessarily the ground state, with respect to the orbital parameters are calculated analytically. The required cofactors up to third order of the overlap matrices over spin-space orbitals in pairs of Slater determinants are calculated by biorthogonalization. All parameters are varied simultaneiously in the direction of the negative gradient (steepest descent). A search logic with dynamically adjusted step-size is shown, in the example of the minimum basis Ne ground state, to find the energy minimum in an efficient manner.
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  • 48
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    International Journal of Quantum Chemistry 10 (1976), S. 181-184 
    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.
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  • 49
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    International Journal of Quantum Chemistry 10 (1976), S. 185-186 
    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 Tab.
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  • 50
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    International Journal of Quantum Chemistry 10 (1976) 
    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
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  • 51
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    International Journal of Quantum Chemistry 10 (1976), S. 191-216 
    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 satisfactory definition of spectral density for the normal modes of lattice dynamics problems requires the study of singular recurrence relations which is carried out in detail for one-dimensional chains with pth neighbor interactions. The relationship of transfer matrices to the dynamical matrix is explored in order to obtain Green's formula. By using Green's formula, a mapping is defined between Vn, whose basis is formed from the normal modes of vibration of an n-particle chain, and V2p, which is the space of boundary conditions for the recurrsion equations. Most of the properties of this mapping may be deduced from a symplectic bilinear form in V2p which is associated with the Hermitean inner product in Vn. This symplectic form defines a geometry which is invariant under the recursion relation, as well as canonical initial and boundary conditions, and a maximal isotropic subspace which may be used to determine square summability of the normal modes and the spectral density in the limit as the number of particles becomes infinite.
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  • 52
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    International Journal of Quantum Chemistry 10 (1976), S. 299-305 
    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: Wave-functions of various spin-dependent and spin-free methods are examined from the point of view of the requirements of the exclusion principle and the spin projection. It is shown that the “two-rowed” or “two-columned” requirements of the standard Young tableaux are necessary but not sufficient to replace the “antisymmetry” requirement of a wave-function and to be regarded as exclusion principle. The symmetry adapted wave-functions which are constructed from the matric basis ers[λ] may not satisfy the exclusion principle and, hence, their usages are open to question. The appropriate symmetry adapted wave-functions which satisfied the exclusion principle are given for any pure spin state. We have also shown that the structure operators NirPir for bond functions are spin projectors in the Waller-Hartree double-antisymmetrized space only, and should not be used in the Hartree product space. Furthermore, if the corresponding matric operators PirNirPir are used in the Hartree product space, then the wave-functions thus constructed may not be antisymmetric with respect to the permutations of indistinguishable electrons.
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  • 53
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    International Journal of Quantum Chemistry 10 (1976), S. 359-377 
    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 error in the author's previous treatment of the interaction of an absorber with high intensity light is noted. The correct development of Mower is applied to determine the amplitude of the initial state of the radiation-matter system. Comparison of the quantum theory solution for a damped absorber exposed to a square light pulse with the results of semiclassical theories based on the undamped optical Bloch equations is effected by determining the effective in- and out-of-phase components of the transition dipole response.In general, the out-of-phase (or absorptive) part of the transition dipole is zero at the outset and strongly time-dependent at short times, evolving to a steady-state value at longer times. For resonance radiation the system exhibits either overdamped irreversible decay or underdamped oscillations, depending upon the relative magnitudes of the incident light intensity and the radiative damping rate. Specific results are presented for a variety of limiting values of the physical parameters, including light intensity, damping rate, and amount of off-resonance.
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  • 54
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    International Journal of Quantum Chemistry 10 (1976), S. 525-542 
    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 representation of an N-electron Schrödinger Hamiltonian on an orthonormal, spin-free (freon) orbital product space is exactly modeled by a second-degree polynomial in the infinitesimal generators of the unitary group. Symmetry adaptation of the orbital product space with respect to the symmetric group yields Gel'fand states which provide base for irreducible represntations of the unitary group. These exist in closed form as, in consequence, does the representation of the model Hamiltonian in this same basis. We retain as physical only those states characterized by tableaux with no more than two columns for which the spin labelling is one-half the difference in the lengths of the two columns. The unitary group formulation is equivalent to standard, number-conserving, second-quantized, many-body theory.
    Additional Material: 1 Tab.
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  • 55
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    International Journal of Quantum Chemistry 10 (1976) 
    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
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  • 56
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    International Journal of Quantum Chemistry 10 (1976), S. 581-598 
    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 systematic method is established for computing the coupling coefficients associated with arbitrary compact groups using only the general properties of the coefficients and the specific character theory of the relevant groups. The basic character theory is first outlined. Then a primitive set of 6j symbols is defined and their computation sketched with careful attention being given to matters of phase fixing. A recursive method is developed for calculating arbitrary 6j symbols using the primitive set. Finally, a primitive set of 3jm factors is set up and then the general 3jm factors computed recursively.
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  • 57
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    International Journal of Quantum Chemistry 10 (1976), S. 559-567 
    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: Quantum chemical CNDO/2 calculations for the conformational preference of the side chain of thioridazine as a function of angle indicated the crystallographically determined structure gave the lowest energy. There is also a small region of conformational flexibility within the first 90° of rotation of the side chain. This is commensurate with the results which we had obtained previously for our similar calculations for promazine and its Cl and CF3 derivatives, perazine and its Cl and CF3 derivatives, and for the hypothetical hitherto unknown N-piperidinopromazine and its Cl and CF3 derivatives. The conformational profile of thioridazine resembles that of the perazines. The calculated gross atomic populations on the alkyl nitrogen in thioridazine was within the range we had previously found necessary for neuroleptic activity.
    Additional Material: 5 Ill.
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  • 58
    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: Ab initio LCAO-MO-SCF Gaussian basis function calculations have been performed for chlorpromazine and promazine. By prescreening for the size of the integrals before calculation, it was only necessary to calculate 12 million out of the possible 38.5 million integrals for chlorpromazine. By a novel procedure of processing the integral tapes for the SCF it was possible to cut down significantly on the amount of time for the SCF. The SCF calculations converged smoothly for both promazine and chlorpromazine. There is a sizeable energy gap between the energy of the highest occupied molecular orbitals in these molecules (which is of the order of -0.3 a.u.) and the lowest unoccupied molecular orbital (which is of the order of + 0.15 a.u.). The gross atomic populations of chlorpromazine and promazine resemble each other and differ only somewhat on the carbon atom to which the substituent is attached and the carbons and their hydrogens adjacent to it.
    Additional Material: 10 Tab.
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  • 59
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    International Journal of Quantum Chemistry 10 (1976), S. 599-613 
    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 various orthogonality and sum rules which the 6j and 3jm symbols satisfy are sufficient to obtain the algebraic formulas for these symbols for SO3 ⊃ SO2. Character theory enters in that the j's and m's occurring in the various sums are given by the triangle rule \documentclass{article}\pagestyle{empty}\begin{document}$$ j_1 \times j_2 = \left| {j_1 - j_2 } \right| \oplus \ldots \oplus \left( {j_1 + j_2 } \right) $$\end{document} together with information on the symmetrized product and the branching, SO3 ⊃ SO2, \documentclass{article}\pagestyle{empty}\begin{document}$$ j \to \left( { - j} \right) \oplus \ldots \oplus \left( j \right) $$\end{document} The resulting calculation is somewhat simpler, algebraically speaking, than previous calculations and has the pedagogical advantage that only the concept of an irreducible representation of a group is required, instead of the more elaborate concept of ladder operators.
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  • 60
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    International Journal of Quantum Chemistry 10 (1976), S. 615-628 
    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 methodology developed in earlier papers is used to compute the 6j symbols and 3jm factors that arise in the group chain SO3 ⊃ T ⊃ C1. The relevant character theory is given and the 2j and 3j symbols calculated. Selection rules are used to predict which j symbols or jm factors are necessarily zero, and then a set of 6j fundamentals computed for T. The complete set of primitive 6j symbols are then computed by application of the orthogonality and Racah backcoupling relations. Primitive 3jm factors are calculated for SO3 ⊃ T and T ⊃ C3 and, from these, all the 3jm factors for T ⊃ C3 and some of those for SO3 ⊃ T computed. A complete table of non-equivalent 6j symbols for T and 3jm factors for T ⊃ C3 is given, together with a table for SO3 ⊃ T of all 3jm factors with j ≤ 2.
    Additional Material: 8 Tab.
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  • 61
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    International Journal of Quantum Chemistry 10 (1976), S. 799-809 
    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: Matrix elements of the Runge-Lenz vector A are presented for those linear combinations of degenerate hydrogenic functions often referred to as hybrid orbitals. The uncertainties in the components of A for each type of wave-function are related to the distribution of classical Kepler orbits corresponding to each function. Matrix elements of A with respect to radially nodeless Slater functions are presented, as these functions are often used as a basis set in atomic and molecular calculations. The properties of A for a piecewise Coulombic central field are discussed in relation to the description of penetrating orbits in the old quantum theory. Simultaneous eigenfunctions of A and the Hamiltonian cannot be chosen for the piecewise Coulombic field because of a discontinuity in the radial derivative of the potential energy.
    Additional Material: 3 Tab.
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  • 62
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    International Journal of Quantum Chemistry 10 (1976), S. 837-852 
    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 method for finding non-relativistic and relativistic wave-functions of an electron moving in the field of a nuclear charge in the jj coupling scheme is proposed. It is based on the usage of generalized spherical functions. The mathematical apparatus necessary to find the expressions for matrix elements of the non-relativistic and relativistic energy or electron transition operators is developed. The formulas obtained for these matrix elements are more convenient than those usually used in jj coupling scheme; only their radial integrals and some phase multipliers depend on orbital quantum numbers.
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  • 63
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    International Journal of Quantum Chemistry 10 (1976), S. 811-835 
    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 orthogonalized plane wave (OPW) method of calculating electronic continuum wave-functions is tested by the computation of photodetachment cross-sections and angular distributions for gaseous halide anions. The results are compared to those obtained by a related augmented plane wave (APW) method involving the exact solution of a single-particle Schrödinger equation containing a piecewise Coulombic potential energy. These comparisons, as well as other involving experimental and theoretical cross-sections from the literature, indicate that OPW cross-sections are, at best, only semi-quantitatively reliable for describing photodetachment even at low photon energies, and that OPW cross-sections should be calculated using the dipole length operator rather than the dipole velocity operator.
    Additional Material: 12 Ill.
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  • 64
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    International Journal of Quantum Chemistry 10 (1976), S. 853-866 
    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: Combined CI-HY method calculations are reported for the ground and first three excited S states of He with an error on the order of 10-7 a.u. within the same 120-term basis. For He 1P, the four lowest states are obtained with an error ≤2 × 10-6 a.u. within the same 102-term basis. H-1 S and 1P states are also treated by the same CI-HY technique. The utility of an spd Slater-type orbital, rijv, v = 0, 1 basis is investigated, with indications that it might be an excellent basis for states of first row atoms.
    Additional Material: 8 Tab.
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  • 65
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    International Journal of Quantum Chemistry 10 (1976), S. 867-872 
    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 many-neighbor approximation (MNA) is a molecular orbital approach in which the nth nearest-neighbor interaction is written in terms of the nth power of the next-nearest-neighbor (NNN) interaction parameter ρ(〈1). By adopting such an approach, an examination is made of the effect of the MN interactions on the crossed-band structure of sp-hybrid crystals. The results obtained show that the MN interactions cause the two allowed bands to expand, with increasing ρ, at the expense of the band gap. The significance of this gap reduction for Shockley surface states is briefly discussed.
    Additional Material: 4 Ill.
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  • 66
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    International Journal of Quantum Chemistry 10 (1976), S. 873-885 
    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 variational principle is derived from the spectral theorem of self-adjoint operators. The principle allows to calculate simultaneously upper and lower bounds for each point of the spectrum. For Schrödinger operators this method of error minimization is reduced to a series of matrix diagonalizations using an iterative process and is linearized in this way. The convergence of this method and the equivalence with the nonlinear problem of variation are proven.
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  • 67
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    International Journal of Quantum Chemistry 10 (1976), S. 887-899 
    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 convergence and the quality of approximation of the variational method developed in part I are tested using the He atom as an example. For the three-body problem the inner products and the norms were explicity expressed as functions of the optimization parameters. The method permits calculation of upper and lower bounds for the ground state of helium.
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  • 68
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    International Journal of Quantum Chemistry 10 (1976), S. 901-908 
    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 PCILO method is used for the study of molecular systems with translational symmetry in a two-dimensional lattice. The calculation for the whole crystal is reduced to the calculation of unit cell pairs. By using the translational symmetry and the first-neighbour approximation, one shows that only four unit cell pairs have to be considered. The procedure described yields the ground-state energy and the charge distribution of the unit cell.
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  • 69
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    International Journal of Quantum Chemistry 10 (1976), S. 909-916 
    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 PCILO method was used to calculate the intermolecular interaction of London-van der Waals type, hydrogen bonding type, and charge transfer type interactions, respectively. The stabilization energies of the calculated supermolecules are: 0.85 kcal · mole-1 for the nonane dimer,4.15 kcal · mole-1 for the water dimer, and3.60 kcal · mole-1 for the butene-2-cis-Li+ complex.The analysis of the individual contributions of the energy reflects well the mechanism of the intermolecular interaction.
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  • 70
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    International Journal of Quantum Chemistry 10 (1976) 
    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
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  • 71
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    International Journal of Quantum Chemistry 10 (1976), S. 917-935 
    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 instabilities, especially the singlet instabilities, of the conventional Hartree-Fock (HF) solutions for a variety of alternant and nonalternant hydrocarbons, some of which have been known to show lattice instabilities (bond-length alterations), are examined. The HF solutions for nonalternant hydrocarbons in the pentalene series larger than heptalene and [4n + 2]-annulenes larger than C22H22 are found to be singlet unstable and there appear new solutions lower in energy than the conventional HF solutions and characterized by charge-density waves exhibiting bond-order alterations. It is found that such symmetry-breaking solutions are energetically further stabilized by distorting the nuclear framework so that it may match up with the distribution of bond-order matrix elements of the charge-density wave, which means that in conjugated systems the singlet instability of the HF solution is always accompanied with the lattice instability. Further, it is shown that in conjugated systems, even when the HF solution is singlet stable, if it is not sufficiently stable as, for example, in pentalene and heptalene, there is every possibility for the occurrence of lattice instability. It is also shown that the singlet instability as well as the lattice instability arises from the existence of a sufficiently low-lying singlet excited state.
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  • 72
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    International Journal of Quantum Chemistry 10 (1976), S. 937-940 
    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 solution is given for the problem of N-completeness which arises in practical calculations for many electron systems because of the necessity of employing a finite basis set of antisymmetric two-particle functions.
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  • 73
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    International Journal of Quantum Chemistry 10 (1976), S. 941-949 
    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 computation scheme is proposed to determine the wave-functions of molecular systems within the framework of the CMC SCF theory and the APSG SCF approach. The orbital optimization is carried out by the refined first-order one-electron Hamiltonian method. Explicit expressions of the first and second energy derivatives are obtained. In the suggested scheme all the calculations are based on using the matrices of the “partial” Coulomb and the exchange operators constructed over the orbitals at the current iteration cycle.
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  • 74
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    International Journal of Quantum Chemistry 10 (1976), S. 951-954 
    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 general harmonic oscillator elements \documentclass{article}\pagestyle{empty}\begin{document}$$ \left\langle m \right|\hat x^s \hat p\left| n \right\rangle $$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$$ \left\langle m \right|\exp \left[ { - \alpha \left( {\hbar /m*\omega } \right)\hat x^2 } \right]\exp \left( {\beta \hat x} \right)\left| n \right\rangle $$\end{document} are derived by a generating function method using operator techniques which contain practically all one- and two-centre integrals with equal frequencies of chemical physics.
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  • 75
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    International Journal of Quantum Chemistry 10 (1976), S. 955-960 
    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 radial moment analysis has been performed for the Hartree-Fock molecular orbitals of the nitrogen molecule. The objective of the analysis was to determine the extent of isovalent hybridization in even and odd sigma molecular orbitals. The radial moment analysis for the LC-SCF-AO fragments of the 2σg, 2σu, and 3σg molecular orbitals substantiates Mulliken's earlier conjecture concerning promotion into 3s atomic orbitals for the 3σg molecular orbital. The concept of free isovalent hybridization is discussed in terms of the atomic orbital shape defined by the extracted moments.
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  • 76
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    International Journal of Quantum Chemistry 10 (1976), S. 961-966 
    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 performed RHF, UHF, UHF with subsequent spin projection, and EHF calculations for the π-electrons of some polyene chains of different lengths in order to investigate the relations among these methods when the number of electrons increases. Special attention is paid to the importance of spin projection for different energetic quantities.
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  • 77
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    International Journal of Quantum Chemistry 10 (1976), S. 1007-1010 
    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 simple proof of the theorem that completely filled shells of fermions do not contain any symmetry component other than the totally symmetric representation is given.
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  • 78
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    International Journal of Quantum Chemistry 10 (1976), S. 1025-1035 
    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 single-determinant open-shell formalism for complex molecular orbitals is developed. An iterative algorithm for solving the resulting secular equations is constructed. It is based on a sequence of similarity transformations and matrix triangularizations.
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  • 79
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    International Journal of Quantum Chemistry 10 (1976), S. 1037-1047 
    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 introduction of symmetry-adapted hybrid atomic orbitals on the metallic atoms allows us to divide the crystal into elementary cells which contain 8 valence electrons each. These cells are described by linear combinations of the halogen valence shell s and p orbitals and the hybrid orbitals of the nearest metallic atoms which point to the halogen. The electronic delocalization of the halogen ions is very weak (≤0.02) for: LiF, NaF, KF, LiCl, NaCI, and KCI. The cell energy in the crystal is obtained by using a first-order perturbative treatment. In agreement with experiment, the f.c.c. type is found more stable than the b.c.c. or the blende type.
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  • 80
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    International Journal of Quantum Chemistry 10 (1976), S. 1049-1056 
    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: Löwdin has formulated a useful criterion for testing the completeness of an expansion basis set. From this criterion one may obtain an incompleteness coefficient for a truncated (finite) basis set. We have investigated the significance of this incompleteness coefficient for some of the basis sets we have used in our recent calculations of bounds to quantum mechanical properties. The similarity of the convergence properties between our bounds and the incompleteness coefficient suggests that Löwdin's criterion is likely to be useful in practice.
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  • 81
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    International Journal of Quantum Chemistry 10 (1976), S. 1057-1059 
    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 energy of the π-electron system in benzene has been obtained by means of valence bond calculations using orthogonal and nonorthogonal basis orbitals at different levels of configuration interaction, which shows the influence of the orthogonalization procedures.
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  • 82
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    International Journal of Quantum Chemistry 10 (1976), S. 1061-1070 
    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 existence of spurious terms increasing as the square of the number of electrons is theoretically proved for the CI treatments of molecules limited to single and double excitations, and is revealed by some numerical calculations (alcanes and juxtaposed hydrogen molecules). An improved perturbation scheme is suggested in order to evaluate the CI energy lowering more carefully. Covergence difficulties are found for larger systems (benzene).
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    International Journal of Quantum Chemistry 10 (1976), S. 1075-1076 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 84
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    International Journal of Quantum Chemistry 10 (1976), S. 1071-1073 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calculations of the electronic energies and wave-functions for the hydrogen molecule D'∏u and B″Σu+ states have been carried out at the estimated curve crossing distance of 1,5307 atomic units. The results show good agreement with previous calculations.
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  • 85
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    International Journal of Quantum Chemistry 10 (1976), S. 1077-1079 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 86
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    International Journal of Quantum Chemistry 10 (1976), S. 1081-1082 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 87
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    International Journal of Quantum Chemistry 10 (1976), S. 123-134 
    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 optimization scheme of the “multiconfiguration method based on the generalized Brillouin theorem” (MCGBT) has been analysed and found to converge quadratically. Its rate of convergence has been compared with that of other optimization methods such as the first-order Rayleigh-Schrödinger perturbation, the steepest descent, the single vector diagonalization, the Newton-Raphson, and the conventional SCF method. The convergence of the MCGBT scheme has been found to be superior to the convergence of the above mentioned schemes.
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    International Journal of Quantum Chemistry 10 (1976), S. 175-179 
    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
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  • 89
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    International Journal of Quantum Chemistry 10 (1976), S. 225-231 
    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: Kronig and Penney's model is used to test a new formulation of quantum virial theorem for periodic systems. It is shown that the corrective term to the usual formulation of the virial theorem corresponding to boundary conditions is of importance and gives correct energy values for the system. Application of the virial theorem to a diatomic molecule also shows an important boundary condition correction if the distance of the nuclei is slightly different from equilibrium position, in accordance with the above correction.
    Additional Material: 1 Ill.
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    International Journal of Quantum Chemistry 10 (1976), S. 233-247 
    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 inhomogeneous operator equation is associated with the equations of motion for ionization- and excitation operators. The partitioning technique is applied to solve the equation. Formal expressions for the ionization- and excitation operators are obtained and examples of approximations to these are given.
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  • 91
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    International Journal of Quantum Chemistry 10 (1976), S. 249-259 
    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 consider the calculation of first-order and second-order atomic and molecular properties from approximate ground-state wave-functions by using variational procedures for solving the first- and second-order perturbation equations. We evaluate the errors in the final results due to the error in the unperturbed wave-function and to the errors caused by the approximations in solving the perturbation equations. By combining slightly different results we can eliminate all first-order errors. Our analysis covers situations where perturbation expansions of the error in the ground-state wave-function are not feasible and it includes the effects due to approximations in solving the perturbation equations.
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  • 92
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    International Journal of Quantum Chemistry 10 (1976), S. 261-280 
    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 densities of states and Fermi energies were accurately calculated from E(k) data obtained by the self-consistent-band Augmented Plane Wave (APW) method, using a quadratic energy expansion. The reliability of the Monte Carlo integration was investigated. It was sufficiently good to determine the anisotropy of the Fermi surface of lithium, sodium, and potassium.
    Additional Material: 8 Ill.
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  • 93
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    International Journal of Quantum Chemistry 10 (1976), S. 393-412 
    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 molecular one-electron Dirac equation is derived by variation of a total energy density functional, whereby the one-electron energies are ascribed a physical meaning. The multiple scattering formalism for molecular systems is relativistically generalized for the determination of molecular four-component spinors. Optimal spinors and one-electron energies for a finite basis set are derived by variation of a functional. The form of the secular equation is very similar to the nonrelativistic form. Using scattering theory, the quantities appearing in the secular equation are interpreted.
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  • 94
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    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 Tab.
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    International Journal of Quantum Chemistry 10 (1976), S. 545-550 
    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: 4 Ill.
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  • 96
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
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    International Journal of Quantum Chemistry 10 (1976), S. 555-557 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 98
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    International Journal of Quantum Chemistry 10 (1976), S. 553-553 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 99
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    International Journal of Quantum Chemistry 10 (1976), S. 552-553 
    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
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  • 100
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    International Journal of Quantum Chemistry 10 (1976), S. 699-714 
    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 developed for determining the allowed states of a many-particle system at definite states of the subsystems (impurity ion complexes in crystals, nucleon clusters in nuclei, polyatomic molecules). The advantage of the method proposed here over those previously developed is that the present one is independent of the number of particles in the subsystems. Depending on the value of spin Sa the subsystems are considered either as bosons or fermions. The representation character expression whose expansion gives all the terms 2s+1Γ(α) with a definite value of total spin of the system is written as the product of permutation and orbital factors. The orbital factor is defined in terms of characters of the local point group representations. Some alternative ways of calculating the permutation factor are discussed: a) with the use of tables of reduction of the unitary transformation group U2Sa+1 in a three-dimensional rotation group; b) through the plethysm coefficients; and c) in terms of 3nj-symbols of three-dimensional rotation group. Some examples of application of the method to various systems are presented.
    Additional Material: 3 Tab.
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