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  • 1
    Electronic Resource
    Electronic Resource
    Direct determination of improved contraction coefficients by a least-squares approach (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 63-71 
    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 simple method is presented for the construction of contracted Gaussian basis sets with little or no energy-optimization. The contraction coefficients are fitted by a least-squares procedure to the orbital expansion coefficients of the completely decontracted basis. The method is applied to the construction of minimum basis sets of first-row atoms from (6s, 3p) uncontracted atomic basis sets, and of [6s, 4p] contracted bases from (12s, 8p) uncontracted bases of second-row atoms. The results are better than using the expansion coefficients directly and are usually comparable to fully energy-optimized bases.The method can also be used to generate balanced atomic contraction coefficients from molecular calculations. This is shown with a (7s, 3p) and a (6s, 3p) basis, both contracted to a minimum basis. The contracted basis sets are employed in several small molecules, and the results are compared with calculations done with the decontracted bases and with contracted bases where the contraction coefficients were energy optimized in the molecules.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200705
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  • 2
    Electronic Resource
    Electronic Resource
    Product of group-function expansions for correlated wave functions (1973)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 7 (1973), S. 187-193 
    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 theorem is proved which demonstrates the relationship between a product of group functions describing the correlated motion of a particular group of electrons in an N-electron system and a wave function obtained from the exact wave function which describes the correlation of the same group of electrons. By considering such products of group functions as elements in a variational wave function, an expansion for correlated wave functions is suggested, which emphasizes the correlated motion of groups of electrons in the whole system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560070205
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of small Gaussian basis sets for ab-initio calculations on biologically active molecules (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 49-61 
    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: (5s, 2p) and (7s, 4p) Gaussian basis sets are presented and evaluated for first- and second-row atoms, respectively, appearing in biologically active molecules. The exponents of the valence shell primitives are taken from larger bases, where the valence shell is better represented, in order to avoid the overemphasis on the core, which occurs in small bases when all exponents are optimized. Contraction coefficients are given for constructing double zeta and minimum molecular basis sets. The basis sets are evaluated by applying them to 19 molecules containing first- or second-row atoms. The results indicate that they are competitive with larger bases for the calculation of properties mainly dependent on the valence shell electrons. In particular, proton affinities seem to be quite reliably reproduced so that they can be used for investigations involving reaction or interaction with proton donors.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200704
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of nonadditivity effects and estimation of many-body effects in linear water chains (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 29 (1986), S. 627-638 
    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: Calculations have been carried out on small linear water chains in order to investigate nonadditivity and cooperativity effects and to study the rate of convergence of the many-body interaction potential. Ab initio wave functions were computed for the pentamer and all related subgroups by using the self-consistent, nonorthogonal group function approximation. The interaction energy and its electrostatic, exchange, polarization, and charge-transfer components were decomposed into a sum of n-body terms. Simple formulas were developed for estimating the interaction energy of higher-order complexes, which also allow an extrapolation to be made to infinite chain length. Comparison of the extrapolated interaction energies, with and without including the nonadditivity effects, showed that the latter increases the H-bond's stability by more than 25%. The results further suggest that the interaction potential can be truncated at either the three- or four-body level, depending on the accuracy required, but that, at best, only rough qualitative results can be expected when pair additivity is assumed. Finally, the dipole moment appears to be sufficiently converged with the inclusion of trimeric terms.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560290406
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  • 5
    Electronic Resource
    Electronic Resource
    Interaction model for the antiinflammatory action of benzoic and salicylic acids and phenols (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 35 (1989), S. 205-214 
    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: Ab initio, quantum chemical methods have been used to develop an interaction model for the binding of benzoic and salicylic acids and phenols to cyclooxygenase, leading to their antiinflammatory action. The model is based on a regression analysis of the energy of the highest occupied molecular orbital with the potency of the active substances to inhibit prostaglandin production in mouse macrophages and on an analysis of the frontier orbital charge distributions and electrostatic potentials of active and inactive compounds. The model suggests that binding is controlled by an electrostatic orientational factor and a charge transfer or polarization contribution. The observed relative potencies of the phenols and acids can be rationalized with the help of the proposed interaction model.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560350113
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  • 6
    Electronic Resource
    Electronic Resource
    Modeling solvent effects in molecular dynamics simulations of proteins (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 291-299 
    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 series of computer simulations has been carried out on bovine pancreatic trypsin inhibitor using various models to mimic the effects of explicit bulk solvent on the structure of the protein. The solvent properties included are the polarization of the solute by the polar bulk solvent and the restraining effect on the motional freedom of the solute due to frictional drag at the solvent-protein surface interface. The former has been included by using a distance-dependent dielectric permittivity to screen the electrostatic interactions, whereas the latter is simulated by adding a limited number of solvent molecules near the protein surface. To achieve the proper mobility of the water molecules, their motion was restrained by adding a harmonic restraining force. It was found that a very small force constant was sufficient to model the static and dynamical behavior of the fully solvated solute, but that it was necessary to include enough explicit waters to occupy the first solvation shell. © 1992 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440215
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  • 7
    Electronic Resource
    Electronic Resource
    Self-consistent, nonorthogonal group function approximation. III. Approaches for modeling intermolecular interactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 811-828 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A new program has been developed for the implementation of the self-consistent nonorthogonal group function (NOGF) approximation for the calculation of wavefunctions between interacting systems. The NOGF approach is based on the reformulation of a single-determinental, closed shell wavefunction into an antisymmetrized product of nonorthogonal group functions, each of which is a single determinant of doubly occupied orbitals. The group product form of the wavefunction combined with the relaxation of the orthogonality constraints and the structure of the orbital equations allows each group's orbitals to be expanded in a local basis set, and makes it possible to modify the orbital expansions or iterative process to simplify the computation. Three models for approximating the full single-determinental wavefunction are tested: (1) different quality basis sets for orbitals belonging to different groups, (2) variation of the types of intergroup interactions included in the wavefunction, and (3) the use of frozen orbitals which have been predetermined in a subsystem and are subsequently transferred to the system of interest. These approximations are applied to the calculation of protonation energies of formate, ammonia, imidazole, and guanidine with part of the first hydration shell being represented by two water molecules hydrogen bonded to each species. The results from different basis sets are compared. Then interaction potentials between the acid and ammonia are calculated for both neutral and charged forms, again with inclusion of part of the first hydration shell. The results show that these techniques can yield reliable wavefunctions of the same quality as obtained with the standard supermolecule approach. The effect of the basis set superposition error in the NOGF approach is briefly considered, and the reduction in computing effort resulting from the three models is discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120706
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