A MOLECULAR DYNAMICS (MD) STUDY OF METHANE IN SILICALITE-1: A NOVEL M0LLER-PLESSET POTENTIAL ENERGY SURFACE

摘要

A novel methane/silicalite-1 potential function for MD simulations has been developed using quantum chemical calculations at a M0ller-Plesset secondary level/ 6-31G basis set. As an application a diffusion coefficient of 5.55x10~(-9) m~2.s~(-1) and heat of adsorption of-5 kcal.moi~(-1) have been obtained for a concentration of one methane molecule per intersection and reasonably match with available studies. In contrary, methane-methane radial distribution functions reveal a first peak at 6.3 A at the low loading (one molecule per intersection) and of 5.4 A at the highest loading (four molecules per intersection) instead of the first peak at about 4 A at all concentrations, and interpreted there as a consequence of methane-methane Lennard-Jones parameters use. It is, then, demonstrated that the appearance of the peak at 4.0 A is caused primarily by an unbalance of the methane/methane and silicalite-1/methane pair potentials. With consistence, the present analysis exhibits favorable resident sites at various concentrations in the zigzag channel.