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  • Springer  (7)
  • 1990-1994  (7)
  • 1994  (5)
  • 1993  (2)
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  • 1990-1994  (7)
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  • 1
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Inelastic neutron scattering and computer modelling techniques have been used to study acoustic phonons in several layer silicate minerals. Experimental measurements have been made on four layer silicate minerals; namely samples of muscovite, Fe-bearing muscovite, margarite and chlorite. The longitudinal acoustic modes propagating along the [0, 0, ξ] direction of muscovite and Fe-bearing muscovite were found to be the same, within experimental error. The longitudinal and transverse acoustic modes propagating along [0, 0, ξ] of muscovite have been calculated using computer simulation techniques based on lattice dynamics. The experimental and calculated longitudinal modes of muscovite are in excellent agreement, thereby demonstrating the complementary nature of both techniques. The shape of both experimental and calculated dispersion curves was found to be approximately sinusoidal, indicating that interatomic forces act principally between nearest-neighbour atoms.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 19 (1993), S. 392-400 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Ab initio LDF theory has been used to derive interatomic potentials for the Si-O and O-O interaction in α-quartz. The potentials have been used to study the lattice dynamical properties of α-quartz from 1 atm to 12.5 Gpa pressure. The results are compared with other calculated and experimentally derived potentials.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 20 (1994), S. 515-518 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Recent experiments (Miller et al. 1987; Bell and Rossman 1992; Bai and Kohlstedt 1992) have shown that olivine, the dominant mineral in the Earth's upper mantle, can contain substantial amounts of water in the form of OH. There is uncertainty, however, as to the mechanisms by which water dissolves into the mineral structure and as to the site it occupies in the host lattice. We have therefore used atomistic computer simulation techniques based on the Born model of solids, to investigate the structures and energies of OH defects in olivine. Our calculations suggest that the most favourable route for incorporation of OH into olivine involves reactions with water accompanied by the reduction of ferric iron for which we obtain a solution energy of 0.46 eV. We propose therefore that the OH content will be largely controlled by the concentration of Fe3+.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 20 (1994), S. 500-503 
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract We have used computer simulation methods to model the structure and energetics of the hydrogarnet defect in grossular. The predicted structure is in good agreement with experimental data. The calculated energy for the reaction of water with grossular to form the hydrogarnet defect is 1.02 Ev (98 kJ mol-1). This low energy of reaction suggests that such defects will be common in garnets where they could play an important role in effecting processes such as atomic transport.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of computer-aided materials design 1 (1994), S. 169-176 
    ISSN: 1573-4900
    Keywords: Zeolites ; Catalysis ; Lattice simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Lattice simulations and quantum mechanical techniques are used to study the energetics involved in the activation of the Ni-zeolite-Y catalyst, which requires migration of the Ni2+ cation from the S1 (hexagonal prism) to the supercage. We show that the barrier to migration of the nickel ions may be overcome by interaction of the migrating ion with molecules such as H2O, NH3 and C2H2 in the supercage, thereby explaining the role of the latter species in the activation process.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 2725-2733 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fluorite structured mixed metal fluorides Rb1−x Bi x F1+2x (0.5≤x≥0.75) are exceptionally good F− ion conductors, a property which is clearly related to the mixed nature of the cation sub-lattice. Extended X-ray absorption fine structure (EXAFS) has been used to study the local structure of the two types of cation in Rb1−x Bi x F1+2x as a function of x. The results reveal marked differences for the local environments of Rb+ and Bi3+. Considerable short-range order develops as x deviates from 0.5, and this can be correlated with the relative conductivities of these materials. Molecular dynamics (MD) has been used to yield complementary information on structural properties. Simulations were performed for a series of temperatures between 80 K and 750 K. Excellent agreement between EXAFS and MD is obtained. A non-collinear interstitialcy mechanism is proposed for anion diffusion, which is seen to be the basis for more complex concerted processes.
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  • 7
    Publication Date: 1994-05-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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