Periodic ab initio study of silico-faujasite

Silico-faujasite (144 atoms in the unit cell) has been investigated using an ab initio periodic Hartree-Fock scheme and an all-electron basis set. The structure has been fully optimized; it turns out that this system is less stable than α-quartz by about 4 kcal mol−1 per SiO2 unit. The electron density and electrostatic potential maps are used for discussing the differences between pores limited by 6- and 12-membered rings in faujasite.