Model Calculations of the Indirect Interaction Between Chemisorbed Atoms

Abstract

When an atom or molecule approaches a clean metallic surface it experiments a translationally invariant potential. After it chemisorbs, however, the charge and spin distributions on the surface have to adjust to the transfer of charge between the two subsystems. These change and spin disturbances, which are reminiscent of the Friedel oscillations, can be of very long range [1] such that if a second atom or molecule now approaches the system it will experiment a non-isotropic potential. It is an experimental fact that a first adsorbate determines a mesh of preferential sites for the chemisorption of a second atom [2]. If the final simultaneous adsorption sites are close enough to each other, the two adsorbates can interact and the local charge and spin distributions for the substrate may be substantially different from twice of those corresponding to the single atom chemisorption case.