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  • Atomic, Molecular and Optical Physics  (3)
  • Wiley-Blackwell  (3)
  • American Association for the Advancement of Science (AAAS)
  • American Chemical Society
  • 1990-1994  (3)
Collection
Publisher
  • Wiley-Blackwell  (3)
  • American Association for the Advancement of Science (AAAS)
  • American Chemical Society
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 557-568 
    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 study of the electronic structure and spectroscopy of models of C60 and C70 cage structures has been carried out using the intermediate neglect of differential overlap (INDO) model Hamiltonian. The geometry for these cages was obtained using gradient-driven methods, and at least in the case of C60, where information is available, is in good accord with the calculations of others. Using a small active space of only single excitations, both configuration interaction (CI) and random phase approximations (RPA) yield spectra in excellent agreement with that obtained from recent experiments. The oscillator strength of the band calculated at ∼47000 cm-1, however, dramatically diminishes as the active space is increased, even though the sum rule increases. We discuss this interesting observation as well as the calculated structure and spectrum of C70.
    Additional Material: 8 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 43 (1992), S. 327-342 
    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 local origin/local orbital (LORG) method of Hansen and Bouman has been implemented with the intermediate neglect of differential overlap Hamiltonian for spectroscopy (INDO/S). The method is shown capable of demonstrating the inductive effects associated with electron-withdrawing substituents through the diamagnetic shielding term. In addition, the method is capable of differentiating chemical shift in differing bond environments. The calculated paramagnetic contribution, however, is deficient for substituents that saturate the minimal basis such as oxygen and fluorine, which severely limits the general utility of the procedure. Through the utilization of reduced linear equations for the paramagnetic term, the method is amenable to any molecule for which a self-consistent field can be performed and therefore can potentially be used to study very large systems. At present, however, the LORG method when used with the rapid INDO/S model Hamiltonian does not reliably reproduce the paramagnetic contribution to the shielding.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 475-486 
    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 examine the effect on calculated oscillator strengths for electronic transitions caused by reintroducing the nodes of valence orbitals in effective core methods through a simple Schmidt orthogonalization. This refinement is then tested within the Intermediate Neglect of Differential Overlap (INDO) model, a valence orbital only model, in both configuration interaction and Random-Phase Approximation (RPA) calculations. It is shown that the differences in oscillator strengths calculated using the dipole-length and dipole-velocity formulations are reduced somewhat for π → * transitions and significantly for n → π* transitions. The oscillator strengths calculated from the dipole-length formalism by the RPA model are in best accord with experiment. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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