Many-Body Effects in Physical Adsorption

We explore the problem of constructing a potential for physical adsorption. The overwhelming majority of such studies assume additivity of the interactions between substrate atoms and gas atoms. We focus on the case of the asymptotic interaction, which assumes an inverse-cube dependence on gas-surface separation. Results from previous evaluations of the coefficient of this function are shown to deviate in a systematic way from those derived from additivity. This screening effect is large; we show how it can be accounted for in terms of the Clausius-Mossotti relation. The results can be applied in a variety of adsorption environments.