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  • 1
    Electronic Resource
    Electronic Resource
    A multicenter numerical integration scheme for polyatomic molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2547-2553 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We propose a simple scheme for decomposition of molecular functions into single-center components. The problem of three-dimensional integration in molecular systems thus reduces to a sum of one-center, atomic-like integrations which are treated using standard numerical techniques in spherical polar coordinates. The resulting method is tested on representative diatomic and polyatomic systems for which we obtain five- or six-figure accuracy using a few thousand integration points per atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454033
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Numerical solution of Poisson's equation in polyatomic molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2993-2997 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have developed a completely numerical scheme for solution of Poisson's equation in multicenter systems. We are thus able to numerically calculate the Coulomb potential of arbitrary charge distributions in polyatomic molecules. The method is based on a decomposition of the multicenter Poisson problem into independent single-center problems, each of which is solvable in standard spherical coordinates. In combination with our multicenter numerical integration scheme reported previously, completely numerical evaluation of arbitrary two-electron Coulomb integrals is possible. Test calculations on the classic two-electron Coulomb and exchange integrals of H2 and the Coulomb interaction energies of several model polyatomic systems indicate that the scheme is both practical and accurate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455005
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Correlation energy of an inhomogeneous electron gas: A coordinate-space model (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1053-1062 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a coordinate-space model for dynamical correlations in an inhomogeneous electron gas. The model treats opposite-spin and same-spin pairs separately, and it also accounts properly for correlation contributions to the kinetic energy. Furthermore, it gives identically zero correlation energy in the case of one-electron systems. Applications to the uniform electron gas and to the atoms H through Ar are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454274
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    On the large-gradient behavior of the density functional exchange energy (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 7184-7187 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A coordinate-space model of the exchange hole density, previously introduced by the author, is extrapolated to the case of very strongly inhomogeneous systems (i.e., large density gradients). As a result, we propose a new gradient-corrected exchange energy functional for application to atomic and molecular problems. The model provides theoretical estimates of the parameters in the functional, and these compare well with empirical values deduced from a least squares fit to exact atomic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451353
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  • 5
    Electronic Resource
    Electronic Resource
    Density functional calculations of molecular bond energies (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 4524-4529 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The calculation of molecular bond energies is a sensitive test of exchange-correlation approximations in density functional theory. The well known local density approximation (LDA) gives excellent bond lengths and vibrational frequencies, but seriously overestimates dissociation energies. Therefore, we have investigated the effect on bond energies of nonlocal corrections to the LDA exchange-correlation functional. We consider the nonlocal correction term of Langreth and Mehl, and also a new semiempirical exchange energy correction. Significant improvements over the LDA dissociation energies are obtained in calculations on first-, second-, and third-row homonuclear diatomic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450025
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  • 6
    Electronic Resource
    Electronic Resource
    Local exchange-correlation approximations and first-row molecular dissociation energies (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 585-594 
    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: Recent Xα calculations of bond energies and other related properties of first-row diatomic molecules show very encouraging agreement with experiment. In the worst cases, however, the Xα dissociation energies overestimate the experimental values by almost 2 eV. Therefore, we have examined several refinements of the Xα theory and their effects on molecular bond lengths, bond energies, and vibrational frequencies. Among them, gradient corrections to the Xα exchange energy and also some variations of the local spin-density correlation energy approximation are considered. We find that a local exchange-correlation functional with gradient corrections gives dissociation energies in significantly better agreement with experiment than the Xα approximation.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270507
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    Paper (German National Licenses)
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