Theoretical study of methane adsorption on graphite

in the present contribution, we performed pm3 semi -empirical and dft calculations of increasing numbers of adsorbed methane molecules on a planar polyaromatic substrate, which mimics a graphene plane. in this way we attempt to describe low coverage methane adsorption on a graphite surface. results show a configuration change of adsorbed molecules from hexagonal to square array as the coverage increases; however methane molecules distance to the surface remains almost unchanged for pm3 and for dft diminishes from 4.2 ？ for one molecule to 3.8 ？.