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  • 1
    Electronic Resource
    Electronic Resource
    Molecular electrostatic fields from bond fragments (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 927-939 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We apply completely transferable, strictly localized molecular orbitals for the calculation of molecular electrostatic fields. This approach, derived from our previous bond fragment method for the calculation of molecular electrostatic potentials, reduces computational efforts drastically. The fields around small molecules containing first- and second-row atoms are systematically overestimated as compared with ab initio calculations with a minimal STO-3G basis set. However, deviations can be corrected by a simple multiplicative factor, which means that the overall shape of the potential and field around the molecule is correctly reproduced. Our approximate field can be used to determine possible hydration sites around molecules as proposed earlier by Peinel and coworkers. Application of the method is illustrated on the formamide molecule.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560310607
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Computational chemistry on a PC (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 38 (1990), S. 163-171 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a package of some IBM PC programs that may find application in computer-aided molecular design. PCGEOM constructs and visualizes molecular models from bond lengths, bond angles, and dihedral angles, from Cartesian coordinates, or from stored fragments. It may prepare output files to be used as input for other programs, like CNDOB (conventional CNDO/2) or PCMEP using the bond increment (BI) method for the calculation of molecular electrostatic potentials. PCPROT is in preparation and will use Protein Data Bank coordinates to visualize and manipulate protein molecular models. Starting from these, it will calculate electrostatic potentials using the BI method and/or monopoles adjusted to reproduce ab initio values for amino acid residues. FSCF is based on a CNDO-type approximation and uses strictly localized molecular orbitals in order to partition large molecules into a central fragment, a polarizable region, and a fully transferable environment. The partition allows one to handle relatively large systems with up to 200 atoms. To illustrate applications, we present estimation of relative inhibitory potencies of a series of substituted triazines on chicken liver dihydrofolate reductase.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560380211
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Rayleigh-Schrödinger perturbation theory for nonlinear Schrödinger equations with linear perturbation (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 47 (1993), S. 469-483 
    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: Rayleigh-Schrödinger-type perturbation theory is developed for the nonlinear Schrödinger equation, which contains a linear perturbation operator. Typical applications involve the self-consistent reaction-field model of solvent effects. Consideration of external perturbations, like electric fields, allows. Calculation of the response properties of solvated species. The general formulae allow development of a consistent Møller-Plesset perturbation theory of solvated molecules. © 1993 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560470606
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Mixed quantum - classical calculations on the water molecule in liquid phase: Influence of a polarizable environment on electronic properties (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 251-265 
    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: Electronic properties of a water molecule embedded in a water droplet are studied in the framework of the generalized self-consistent reaction field approach, using ab initio Hartree-Fock and configuration interaction wave functions. Electrostatic and inductive effects of the surrounding water molecules were calculated with the help of configurations drawn from a classical molecular dynamics simulation. Basis-set effects and solute-solvent interaction operator representation are examined. Embedding energies and liquid-phase multipole moments obtained from the present mixed quantum-classical model are compared with corresponding quantities for purely classical water models. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    A comprehensive approach to molecular charge density models: From distributed multipoles to fitted atomic charges (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 17-37 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some alternative methodologies for the construction of reliable charge density models, involving distributed multipole schemes, potential fitted atomic charges, and a recent approach proposed by Ferenczy, are compared and analyzed critically. Ferenczy's method, which combines the distributed multipole description and the classical least-squares fit, allows one to get an insight into the well-known shortcomings of standard potential- or field-derived atomic charge models. It is now demonstrated that the conformational dependence of fitted point charges is not exclusively due to through-space inductive effects, but that it can be partly rationalized by the reorientation of the atomic multipoles. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520104
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  • 6
    Electronic Resource
    Electronic Resource
    Critical analysis of electric field modeling: Formamide (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 1234-1245 
    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 detailed analysis of ab initio derived electric field and multipole modeling is presented using formamide as an example. Penetration effects, a problem encountered with most currently used modeling methods, are avoided using the Overlap Multipolar Expansion (OME) technique computed up to the hexadecapole level. This method is shown to be grid insensitive. The OME fields and subsequent atomic charge modeling are found to be more sensitive to correlation effects than to basis sets changes. Three different types of error analysis are applied to test the accuracy of regenerated fields from various multipole descriptions. It is shown that atom centered charge models, those most commonly used in the literature, have significant errors. Considerable improvement can be made by using various combinations of charge, dipole, and quadrupole atom- or bond-centered models. For molecular dynamic programs it is argued that the best compromise between accuracy and efficiency is to use both atom and fictive atom charge models calculated from MP2 level density matrices using at least DZP level basis sets. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540131007
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    Paper (German National Licenses)
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