Theoretical study of the structure and properties of Na-MOR and H-MOR zeolite models

This work presents calculated structural parameters and energetic properties of Na- and H-mordenites (MORs) using cluster models with more than 400 atoms. These state of the art calculations were performed within the framework of density functional theory, using both the local density approximation and the generalized gradient approximation, employing all-electron basis sets. The most populated T3, T4, and T1 Al sites have been investigated using two different MOR models, each containing two isolated Al sites. A detailed analysis of the structures, three-dimensional contours of molecular electrostatic potential, binding energies of Na cations and protons, and BrØnsted O-H harmonic frequencies are presented. These properties are compared with available experimental results. The structural changes among Si/Al substitution as well as Na/H exchange are discussed.