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  • 1
    Electronic Resource
    Electronic Resource
    V4+ doping into SiO2, ZrO2 and ZrSiO4 structures. An ab initio perturbed ion study (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 175-186 
    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: An ab initio perturbed ion study using X-ray diffraction data has been carried out for ZrSiO4 (zircon), ZrO2 (monoclinic zirconia, baddeleyite), and SiO2 (α-cristobalite) crystal lattice structures. The different substitutions of V4+ for Zr4+ and Si4+ occurring in these host lattices have been analyzed. Geometry optimizations have been performed with the aim of determining the relative stability, cell parameters, and force constants of radial displacement associated with the local relaxation for pure and doped structures. Numerical results are confronted against experimental data and compared with previous results. The geometrical cell parameters of different structures obtained by computer simulation and the results of the X-ray diffraction studies agree with previous experimental data. For the zircon lattice, the substitution of V4+ for Zr4+ at an eightfold-coordinated site is energetically favorable while the substitution of V4+ for Si4+ at a fourfold-coordinated site is unstable. For ZrO2, the substitution of V4+ for Zr4+ is energetically favorable while the substitution of V4+ for Si4+ in SiO2 is energetically unfavorable. There is less sensitive influence of the crystal lattice parameters for substitutions occurring at the eightfold-coordinated ion site in ZrSiO4 and SiO2 structures. The doping process produces a decrease of force constant (k) values associated with the breathing fundamental vibrational mode for all structures. The k associated with the radial displacement in dodecahedral substitution in the ZrSiO4 structure is especially high. The force constants for this movement in tetrahedral substitution in the ZrSiO4, ZrO2, and SiO2 structures have a lower value. The differences between ionic radii reported by Shannon and Prewitt of the species concerned in the doping process are not capable of explaining the relaxation of crystal lattice parameters in the ZrO2 and SiO2 structures. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480820
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  • 2
    Electronic Resource
    Electronic Resource
    ZnO clusters models: An AM1 and MNDO study (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 643-653 
    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: AM1 and MNDO semiempirical electronic calculations have been carried out for ZnO surface ((ZnO)n, n = 11, 16, 22, 24, 33, 42, and 44) cluster models. The theoretical results can be summarized as follows: (i) the energy gap HOMO-LUMO is shown to be dependent on the cluster size and geometry optimization; however, better agreement of this gap with experimental data is obtained with cluster of limited size (n = 16, 22, and 24). (ii) The Mulliken charge of the cluster zinc ion is invariant with the optimization procedure, showing an average value of 0.52 a.u. (MNDO) and 0.62 a.u. (AM1). © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480858
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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