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  • American Institute of Physics (AIP)  (2)
  • 1990-1994  (2)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4215-4224 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A series of ab initio self-consistent-field molecular orbital (SCF-MO) calculations, on defect centers involved in radiation damage of α quartz, is reported. Calculations were performed on a 21 atom cluster (Si5O12−16), using a 3–21 G basis set. The long-range Coulomb interactions of α quartz were included, by surrounding the 21 atom cluster with 956 point charges, so that on geometry optimization, the characteristic features of α quartz were maintained. Various defect centers containing Al3+ substitutional ions, and their compensating electron-hole and proton defects were studied. The results obtained for the [AlO4]0 center are in close agreement with electron spin resonance (ESR) data. Calculations were also performed on the oxygen vacancy and related defects, such as the E'1 and E4 defects, where qualitative agreement with ESR results was obtained. An assessment is made, of the effect of including long-range Coulomb interactions, by comparison with other SCF-MO cluster models of these systems, which do not include these electrostatic effects.
    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 93 (1990), S. 3573-3579 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The problem of deriving realistic interaction potentials for modeling hydrated sites within aluminosilicate structures has been considered. It is argued that since a variety of cationic sites is involved, the effect of the lattice must be taken into account explicitly, both in the derivation and in the use of H2O–cation potentials. A new method for doing this is described with examples for H2O–Si4+ and H2O–Al3+ in quartz and/or zeolite-A. A more detailed analysis for H2O–Ca2+ in zeolite-A and cement structures is presented.
    Type of Medium: Electronic Resource
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