Adsorption of single Ag and Cu atoms on regular and defective MgO(001) substrates: an ab initio study

The DFT slab calculations were performed for Ag and Cu atoms adsorbed on both regular and defective MgO(001) substrates. Both metal atoms and surface O vacancies (F-s centers) were distributed uniformly with a concentration of one Ag, Cu or F-s per 2 x 2 surface supercell. Surface O2- ions are energetically more preferable for metal-atom adsorption on a regular substrate as compared to Mg2+ ions. The nature of the interaction between Ag or Cu adatoms and a defectless MgO substrate is physisorption (despite the difference in the adsorption energies: 0.62 vs. 0.39 eV per Cu and Ag adatom, respectively). Above the F-s centers, metal atoms are bounded much stronger when compared with regular O2- sites (2.4 vs. 2.1 eV per Cu and Ag adatoms, respectively). This is accompanied by a substantial charge transfer towards each adatom (Deltaq(Cu) = 0.41 e and Deltaq(Ag) = 0.32e) as well as a formation of partly covalent Me-F-s bonds across the interface (Mulliken bond populations p(Cu-Fs) = 0.25e and PAg-Fs = 0.33e). (C) 2004 Elsevier Ltd. All rights reserved.