Elastic and structural properties of zeolites: Sodalite and dehydrated zeolite A

Apairwise interatomic potential has been used to investigate elastic and structural properties of two cubic zeolites: sodalite and dehydrated zeolite A. Constant volume energy minimization has been used to determine the variation of lattice constants and atomic coordinates with pressure. The calculated structures of sodalite and dehydrated zeolite A obtained at zero pressure are in reasonably good agreement with the available experimental values. We find that the structures at zero pressure are largely determined by the Coulomb potential. The pressure dependence of bond lengths and bond angles show that both sodalite and dehydrated zeolite A are easily deformed by bending the Si-O-Al angles. As expected for a less dense crystal, the dehydrated zeolite A is softer than the sodalite. We have also obtained the equation of state of these materials.