Substrate screening of the interaction between adsorbed atoms and molecules: Ne, Ar, Kr, Xe, and CH4 on graphite

This paper treats the electrodynamic screening by the substrate of the van der Waals interaction between adsorbed particles. The free-space interaction is modified by a perturbation V, which describes the effect of the substrate. The McLachlan expression for V is evaluated for the cases of Ne, Ar, Kr, Xe, and CH4 adsorbed on graphite basal planes, and a potential energy between adsorbed molecules (atoms) is calculated. The main effect is a reduction in well depth of 15-20% from the free-space values. Experimental data are semiquantitatively consistent with these potentials. Discussion of the results and their implications is given.