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

Abstract

We report here the results of our density functional theory calculations at local density and nonlocal density approximation levels and Hartree Fock–self consistent field calculations on disilicic acid type cluster models representing faujasite zeolite lattice. The geometric parameters 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 calculations. The predicted geometric parameters are reasonably close to the experimentally reported values, wherever available, except for the slightly overestimated Si–O bond distances. The influence of the geometric 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.