Intensities of the vibrational spectra of siliceous zeolites by molecular dynamics calculations. II - Raman spectra

Three models based on electro-optical parameters were tested for the calculation of the Raman intensities of the vibrational modes deduced from (molecular dynamics) calculations on four siliceous zeolites: sodalite, faujasite, zeolite A and silicalite. The best results were obtained from the electro-optical model containing three parameters: the derivatives of the longitudinal and transversal polarizabilities of the SiO bond with respect to the SiO bond length and the anisotropy of the polarizability tenser of the SiO bond. These parameters permit the reproduction of the relative intensities over the whole wavenumber range. The bond stretching range over 700 cm(-1) is driven by the first two parameters, whereas the equilibrium anisotropy participates significantly in the very low wavenumber region. Copyright (C) 2001 John Wiley gr. Sons, Ltd.