Embedding method to simulate single atom adsorption: Cu on Cu(100)

Within full relativistic four-component ab initio density functional calculations we examined the adsorption of a Cu adatom on a Cu(100)-surface. The surface was simulated by a cluster of Cu atoms in which the number of atoms was successively increased to 99 atoms. Through extensive studies we were able to get convergence in adsorption energy and bond distance with about 60 atoms. Using converged cluster sizes, the results of the binding characteristics are in good agreement with other solid-state calculations. The same adsorption process was then studied with much smaller clusters that were embedded into different types of environments. By this scheme we were able to reproduce the same converged results with a decreased cluster size of only about 25 embedded atoms.