THE RELATION BETWEEN ZEOLITE FRAMEWORK STRUCTURE AND VIBRATIONAL-SPECTRA

Using a general valence force field method, infrared and Raman spectra of pure silica zeolite crystals and molecular substructures of zeolites are calculated. Computed spectra of the substructures are directly compared with computed spectra of the crystal. Also, a comparison of the atomic displacement vectors of the vibrational modes is made. No general theoretical basis for a correlation between the presence of large structural elements and spectral features, sometimes reported, is found to exist. An extensive comparison between experimental and theoretical infrared and Raman spectra of the SiO2 forms of sodalite and faujasite is made. Other applications of vibrational spectroscopy to zeolite structure research, such as the Si-O-Si angle distribution and the location of acid sites, are evaluated as well.