The significance of many-body interactions in physical adsorption

Abstract

The significance of many-body interactions in the physical adsorption of rare gas atoms on solid surfaces has been investigated. A simple model of the system was considered in which the atoms of the solid and the adsorbed atom were represented by interacting isotropic point dipoles. The fullN-body interaction energy between the adsorbed atom and the solid was calculated exactly to lowest order in the expansion parameter [αα0ηπ(ω0/ω)2]/4d 3 (ω, α and ω0, α0 are the solid atom's and adsorbed atom's characteristic frequency and polarizability,d is the distance from the surface of the adsorbed atom, and η is the number of atoms per unit volume in the solid). The interaction was then evaluated for the adsorption of various rare gas atoms on rare gas solids. It was found that the fullN-body interaction deviated at most by only2 1/2% from the interaction obtained by considering only two-body interactions. In addition, it was found that a finite expansion in two-, three-, ... body expressions may lead to erroneous results for the interaction energy since extensive cancellations occur between successive terms of the series.