Investigation of TO₄ Tetrahedra in X,Y Zeolites by Vibrational Properties

The infared spectra of zeolites have been widely studied and the vibrational bands have been empirically interpreted as being characteristic of various "internal" TO₄ motions and the motions of some "external" linkages of the three-dimensional framework. We use the normal coordinate analysis to deal with the internal vibration and its varying with Si/Al ratio. We get the relationship between Si/Al and bond length as well as frequencies of asy. and sym.. By adjusting the force constants of stretching, bending and str-str interaction, we find the mutual linear relations between T-O stretching constants, bond lengths and Si/Al ratio, and we also find the change of the bending constants being very small.