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  • American Institute of Physics (AIP)  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 3397-3407 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Several additions to the pseudospectral Hartree–Fock theory are described, including a localized least-squares procedure, various numerical cutoff algorithms, and calculation of all integrals in the diatomic frame. This pseudospectral method is tested on 23 molecules, ranging in size from two to twenty atoms (200 6-31G** basis functions). A direct comparison of accuracy and computational efficiency is made with the conventional electronic structure programs gamess, gradscf, gaussian 86, and gaussian 88. The pseudospectral code is shown to be up to nine times faster than any of the above programs for the molecules tested here; moreover, this timing advantage increases with molecular size, suggesting that ab initio calculations may soon be possible on large systems not accessible by the Roothaan–Hall procedure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 3627-3633 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Linear-response theory is used to derive a microscopic formula for the free-energy change of a solute-solvent system in response to a change in the charge distribution of the solutes. The formula expresses the change in the solvent polarization energy as a quadratic function of the changes in the partial charges at the atomic centers of the solute atoms. The average electrostatic potential at the sites of the solute charges and the second moment of the fluctuations in the electrostatic potential at these sites enter as parameters in the formula. These parameters can be obtained from computer simulations of a reference system with fixed solute charges and the results then compared with explicit free-energy simulations of the corresponding processes or with experiment. The formula provides a microscopic definition of the dielectric response function for the combined solute plus solvent system which can be related to standard formulas for the dielectric response. A simple numerical example involving a simulation of the charging free energy of two ions in aqueous solution is discussed. The change in the solvent polarization with solute charge predicted using the molecular dielectric response function agrees remarkably well with the results of corresponding free-energy simulations for large changes in the solvent polarization energy. Some applications of the molecular dielectric response formula are discussed.
    Type of Medium: Electronic Resource
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