THE INFLUENCE OF THE GEOMETRIC PARAMETERS ON THE ELECTRONIC-PROPERTIES OF FAUJASITE CLUSTER-MODELS AS DERIVED FROM DENSITY-FUNCTIONAL THEORY AND HARTREE-FOCK SELF-CONSISTENT-FIELD METHODS

We report here the results of our density functional theory calculatio ns at local density and nonlocal density approximation levels and Hart ree Fock-self consistent field calculations on disilicic acid type clu ster models representing faujasite zeolite lattice. The geometric para meters such as Si-O and Al-O bond distances and Si-O-Si, Si-O-Al, O-Si -O and O-Al-O bond angles are derived from the geometry optimization c alculations. The predicted geometric parameters are reasonably close t o the experimentally reported values, wherever available, except for t he slightly overestimated Si-O bond distances. The influence of the ge ometric parameters on the electronic properties such as total energy, dissociation energy of charge compensating cations and the net charge on bridging oxygen are studied in detail. (C) 1998 Elsevier Science B. V.