Construction of a potential energy surface for molecular dynamics studies of methane adsorbed in zeolites

A potential for the interaction of methane molecules with the framework atoms of siliceous zeolites is developed empirically. The CH4 molecule is considered in the spherical approximation. The interaction potential includes repulsion, dispersion, and induction energy. It is shown that even if the effective charges on the framework oxygen and silicon atoms are large, the contribution of the induction energy is weak in comparison with those of dispersion and repulsion energies due to compensation effects. The calculated parameters of a Lennard-Jones potential are compared with those used in previous MD calculations. As an application we calculate diffusion coefficients and the heat of adsorption of methane in silicalite which can be compared to available experimental data.