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  • 1
    Electronic Resource
    Electronic Resource
    Interlayer Porosity in Montmorillonite Intercalated with Keggin-like Cation Studied by Molecular Mechanics Simulation (1997)
    Springer
    Journal of molecular modeling 3 (1997), S. 467-472 
    Details
    ISSN: 0948-5023
    Keywords: Keywords: Molecular mechanics ; Intercalated clays ; Keggin cation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics simulation using Cerius2 modeling environment have been used to investigate the structure of montmorillonite, intercalated with Keggin-like cation7+. Present work is focused to the strategy of modelling in case of intercalated layered structures and to investigation of structure parameters characterizing the interlayer porosity, that means: the interlayer distance, the position, orientation and distribution of Keggin cations in the interlayer space and the stacking of layers. Molecular simulations revealed the structure of the interlayer and led to the following conclusions: In the most stable configuration the 3-fold axis of Keggin cation is perpendicular to the silicate layer. This orientation of Keggin cations leads to the basal spacing 19.51 (10-10 m). Energy minimization during the translation of Keggin cation along the silicate layer gives only small fluctuations of basal spacing and no correlation has been found between the shift of cation along the layers and the value of basal spacing. No systematic relationship has been found between the shift of cation and crystal energy and no systematic relationship exists between the mutual shift of two successive layers and the values of basal spacing and crystal energy. Consequently, no two-dimensional ordering of Keggin cations in the interlayer and no regular stacking of layers can be expected. X-ray diffraction diagrams obtained for montmorillonites, intercalated with Keggin cation, confirm present conclusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s008940050064
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  • 2
    Electronic Resource
    Electronic Resource
    Montmorillonite and Beidellite Intercalated with Tetramethylammonium Cations (2000)
    Springer
    Journal of molecular modeling 6 (2000), S. 600-607 
    Details
    ISSN: 0948-5023
    Keywords: Intercalated clays ; Tetramethylammonium-clays ; Modeling ; Molecular mechanics ; Montmorillonite ; Beidellite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics simulations, combined with X-ray powder diffraction and infrared spectroscopy, have been used in structure analysis of montmorillonite and beidellite intercalated with tetramethylammonium cations. A complex structure analysis provided us with the detailed structure model, including characterization of the disorder, the total sublimation energy and a charge distribution in the structure of intercalates. The calculated basal spacings (14.36 Å for TMA-montmorillonite and 14.12 Å for TMA-beidellite) are in good agreement with the experimental values (14.31 Å for TMA-montmorillonite and 14.147 Å for TMA-beidellite). Both intercalated structures exhibit positional and orientational disorder in the arrangement of TMA cations, and consequently disorder in layer-stacking. In the present work we analyse the effect of octahedral and tetrahedral substitutions in a 2:1 silicate layer on the arrangement of tetramethylammonium (TMA) cations in the interlayer space of montmorillonite and beidellite. The most significant difference between TMA-montmorillonite and TMA-beidellite is in the charge distribution on the TMA cations and silicate layer. The TMA-beidellite structure is highly polarized, the total charge on one TMA cation is +0.167 e−, while the total charge on the TMA cation in montmorillonite is +0.050 e−.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0089400060600
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  • 3
    Electronic Resource
    Electronic Resource
    Water/Ethanol Displacement Reactions in Vanadyl Phosphate (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2289-2294 
    Details
    ISSN: 1434-1948
    Keywords: Intercalations ; Vanadyl phosphate ; Ethanol ; Hydration ; Kinetics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The course of the replacement of ethanol by water molecules in the VOPO4·2C2H5OH intercalate, and of water by ethanol in VOPO4·2H2O has been studied by X-ray diffraction and infrared and Raman spectroscopy. Formation of mixed phase VOPO4·C2H5OH·H2O was not observed. The shape of the kinetics curves indicates a transition of at least one reaction zone through the crystal. A delay in formation of the product in comparison with the decrease in the amount of starting material can be explained by the existence of non-diffracting advancing phase boundary. In a VOPO4/ethanol/water system, VOPO4·2C2H5OH is formed as the only product when the system contained more than 96 vol% of ethanol, whereas in the system with less than 94 vol% of ethanol only VOPO4·2H2O is present.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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