Ab initio generalized valence force field for zeolite modelling 2. Aluminosilicates Original Research Article

A generalized valence force field for modelling the vibrational spectra of aluminosilicates is developed on the basis of ab initio calculations (3-21G∗ and DZP/MP2) performed on small clusters: Si(OH)4, (OH)3SiOSi(OH)3, Al(OH)−4, H3SiOHAlH3, (OH)3SiOAl(OH)−3 and (OH)3SiOHAl(OH)3. The Cartesian force constants from the ab initio calculations are transformed into internal coordinates and used in molecular dynamics simulations of protonated and non-protonated faujasite structures. Calculated positions of the bands in the infrared and Raman spectra of the zeolite are in good agreement with those observed. The force field explains the main features in the vibrational spectra OH(OD) groups of protonated structures.