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  • 1
    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 kinetics of gas-phase electron transfer reactions for a variety of metal-containing reactants have been studied by using Fourier transform ion cyclotron resonance mass spectrometry. Classes of ion/molecule processes studied include both self-exchange (thermoneutral) and exoergic cross reactions. The molecules investigated include metallocenes and octahedral coordination complexes of the transition elements. In a few cases, direct comparisons of condensed-phase and gas-phase reactivities can be made. The experiments with octahedral coordination complexes are the first studies of Werner-type metal complexes in electron-transfer reactions in the gas phase. Simple theoretical models involving unimolecular rate theory, classical reorganization barriers, and quantum mechanical approaches are used to rationalize the dependence of the overall rates of these reactions on the molecular properties of the reactants. In particular, the role of Franck-Condon factors in charge-transfer reactions is examined, and theoretically estimated factors are compared with experiment for a typical metallocene, ferrocene.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 195-207 
    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: Chemical and biological damage, caused by directly or indirectly ionizing radiations, is attributable to the action of the charged particle tracks in the absorbing medium. Attempts to elucidate the biophysical mechanisms involved, and to quantify the damage, are typically made in terms of one or more of the main physical parameters descriptive of the charged particle tracks. To meet a need for a ready reference source of such information, tables of the relevant parameters have been calculated for a liquid water medium. The full tables are obtainable elsewhere. Here, a description is given of the quantities calculated and an extended example is given of their application in elucidating the physical mechanisms of radiation-induced biological damage. A representative selection of data is displayed graphically to illustrate the extent of the information obtained and its value in, e.g., application to fundamental radiation dosimetry. Track structure data is tabulated for instantaneous energies of individual particles and for the fluence and dose-weighted spectra at charged particle equilibrium. Data are listed for incident electrons (50 eV to 30 MeV); characteristic Kα X-rays from carbon to uranium; commonly used radioisotope sources of 241Am, 137Cs, and 60Co and for continuous X-ray spectra (≤300 kV); Auger electron and beta-emitter radionuclides; heavy charged particles having specific energies of 0.5 keV/μ to 1 GeV/μ for 74 ion types ranging from protons to uranium ions, and for monoenergetic neutrons (0.5 keV to 100 MeV). Quantities listed are kerma factors; fluence of charged particles per unit source concentration; buildup factors; track and dose-average LET and restricted LET; W values; z2/β2;β2; delta-ray yields, energies, and ranges; ion ranges; and the mean free path for primary ionization and the linear primary ionization. For indirectly ionizing radiations, the microdose quantities, frequency, and dose means of lineal energy are tabulated along with typical energy deposition distribution spectra for neutrons and gamma rays in micron and nanometer volumes. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 600-603 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio calculations employing a standard double-zeta basis set augmented with various polarization functions have been used to investigate the lowest energy region of the ground-state potential energy surface of the formamide molecule. Hartree-Fock calculations with only d polarization functions on the nonhydrogen atoms located two stable minima, that with geometry distorted from planarity having slightly lower energy; only one stable minimum with planar structure is found when p polarization functions on the hydrogens are included. In contrast optimizations, which account approximately for the correlation energy using second-order Møller-Plesset perturbation theory consistently favor a single slightly nonplanar minimum energy geometry.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 58-63 
    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 simple extension of the Newton-Raphson method is proposed that approximately accounts for anharmonicity in bond-stretching coordinates. By modeling each bonded distance in a polyatomic molecule as a Morse oscillator with no anharmonic stretch-stretch or stretch-bend coupling, a multiplicative correction factor to the Newton-Raphson step is derived. Representative examples suggest that the rate of convergence of the proposed scheme is typically faster than that of the standard Newton-Raphson method.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 972-977 
    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 quadrature-point-driven implementation of the standard Rys polynomial method for computing two-electron repulsion integrals of gaussian basis functions has been found to be both concise and openended with respect to the angular momentum of the gaussian functions (i.e., s,p,d,f,g,…). These are important features in certain applications, such as molecular properties and property gradients.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 49 (1994), S. 559-573 
    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: Use of orthogonalized Hartree product (OHP) orbitals as the reference orbitals in coupled-cluster (cc) calculations is presented. Since such orbitals are determined without exchange, they provide as “classical” a description as possible. The OHP orbitals were generated by implementing Harris's formulation of the original Hartree method. Some computational considerations of the formulation are discussed. A critical evaluation of the OHP method as an orbital localization scheme is presented. The OHP orbitals were used as the reference in CCD and CCSD calculations and compared with corresponding Hartree-Fock (HF) reference CC results. The average variation of localized Hartree product (LHP) reference CCSD energy from that of the HF reference is 0.83 kcal/mol, whereas for CCD, the average variation is 234 kcal/mol, indicating the importance of single-excitation effects in CC calculations with non-HF references. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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