Embedded cluster approach to simulate single atom adsorption on surfaces: Cu on Cu surface

Within full relativistic four-component ab initio density functional calculations, we examined the adsorption of a Cu-adatom on a Cu(1 0 0)-surface. As a first step we simulated the surface by a cluster of atoms and increased the size successively up to nearly 100 atoms. We found that using more than 60 atoms causes no significant changes in adsorption energy and bond distance. In a second step we used an embedding approach where a relatively small cluster was embedded in different types of environments. With only 26 embedded Cu-atoms we were able to reproduce the converged values we had calculated before and which are in good agreement with other solid-state calculations.