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Abstract

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.