MINIMUM ENERGY CONFIGURATIONS OF ATOMS ADSORBED ON A LATTICE

Abstract

The minimum energy arrangements of atoms adsorbed on a crystalline surface display a very rich set of geometries originated from the competition between the adsorbate-adsorbate interaction, and the tendency to occupy the most favorable adsorption sites over the substrate. We develop a method to obtain these geometries for rational coverages assuming the adsorbates occupy symmetric sites and that they form a lattice commensurate with the substrate, allowing for multi-atomic primitive cells. We obtain results for adsorption on a square lattice with truncated-dipolar interactions. We propose a new truncation scheme which we compare with previous ones, and we explore the effects of changing the range of the potential. The ordered phases we obtain agree with experiments performed for K over Ir(001) and Cs over Rh(001). Furthermore, our results supply some insight on the absence of observed ordered phases for some rational coverages.