First-principles slab calculations were performed for Ag and Cu adsorption on periodically distributed point defects (a single O2- or Mg2+ vacancy per 2x2 surface super-cell) on a non-polar MgO(001) substrate. Using this procedure, Fs and Vs centers were both modelled by retaining in the vacancy the basis set of the missing O2- and Mg2+ ions, respectively, with local relaxation of the nearest substrate ions. Adsorption of metal atom over the Fs center (2.4eV versus 2.1eV per Cu and Ag adatom, respectively) was much stronger as compared with regular O2- sites (0.6eV versus 0.4eV, respectively). The Fs center donated a substantial charge to Ag and Cu adatoms (0.3 to 0.4e) as well as forming covalent bonds with them; with similar bond populations. When a metal adatom approached the Vs center, it donated 1.0 to 1.1e towards the nearest surface O2- ions. Its binding energy (10.0 versus 9.6eV per Cu and Ag adatom) was markedly larger than that over the Fs center. The interfacial distance in the former case was quite small (0.16 to 0.23Å) and the metal adatom thus almost replaced a missing Mg2+ ion.

Coin Metal Adsorption on Defective MgO(001) Surface - ab initio Study. Y.F.Zhukovskii, E.A.Kotomin: Physica Status Solidi C, 2005, 2[1], 347-50