Coin metal adsorption on defective MgO(001) surface: ab initio study

Abstract

First principles slab calculations have been performed for Ag and Cu adsorption on periodically distributed point defects (a single O2– or Mg2+ vacancy per 2×2 surface supercell) on the non-polar MgO(001) substrate. Using the procedure implemented in the CRYSTAL-03 code, both Fs and Vs centers were modeled by retaining in the vacancy the basis set of the missing O2– and Mg2+ ions, respectively, with the local relaxation of the nearest substrate ions. Adsorption of metal atom over the Fs center (2.4 eV vs. 2.1 eV per Cu and Ag adatoms, respectively) is much stronger as compared with regular O2− sites (0.6 eV vs. 0.4 eV, respectively). The Fs center donates a substantial charge towards Ag and Cu adatoms (0.3-0.4 e) as well as forms covalent bonds with them, with similar bond populations. When metal adatom approaches the Vs center, it donates 1.0-1.1 e towards the nearest surface O2– ions and its binding energy (10.0 eV vs. 9.6 eV per Cu and Ag adatoms) is markedly larger than that over the Fs center. Moreover, the interfacial distance in the former case is quite small (0.16-0.23 A), thus metal adatom almost substitutes a missing Mg2+ ion. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)