Simple Rules to Predict the Structure of Adsorbed Gases on Crystal Surfaces

Abstract

The surface structures of adsorbed gases on crystal surfaces which were detected by low-energy electron diffraction have been reviewed. From the analysis of the available structural data three rules of ordering have been proposed. The close-packing rule indicates that adsorbate–adsorbate interaction plays an important role in ordering. The rules of rotational symmetry and similar unit cell vectors are the consequence of the substrate–adsorbate interaction. Judicious application of these rules should allow one to predict the surface structures of adsorbed gases and condensable vapors which would form on crystal surfaces. It appears that both the heat of adsorption and the activation energy for surface diffusion of the adsorbed molecules influence ordering on surfaces.