Knowledge Bank

Infrared spectroscopy has been widely used to study zeolites and vibrational bands have been empirically assigned. We have chosen $T10O12$ (T-Si. Al) as a basic model of the DSR unit in ZSM-5 zeolite, and calculated it by four kinds of previous force fields, but none seems satisfactory. This is because these previous force fields come from studies of silicates. So we have combined Badgen's force field with Batsarov's. The results are in good agreement with the observed frequencies. We have also used the normal coordinates to study the $TO4$ tetrahedron and its variation with SUAI ratio in X Y zeolites. We get the relationship between the bond length and SUAI as well as frequencies. By adjusting stretching, bending and interaction constants we obtain a linear relationship between the T-O stretching constant and SUAI ratio: $FR=2595\times N4E/(N4E+NSI)+5.587.$ The changes in the bending constant are very small.