Adsorption of single Ag and Cu atoms on regular and defective MgO(0 0 1) substrates: an ab initio study

Abstract

The DFT slab calculations were performed for Ag and Cu atoms adsorbed on both regular and defective MgO(0 0 1) 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 2×2 surface supercell. Surface O 2− ions are energetically more preferable for metal-atom adsorption on a regular substrate as compared to Mg 2+ 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 O 2− sites (2.4 vs. 2.1 eV per Cu and Ag adatoms, respectively). This is accompanied by a substantial charge transfer towards each adatom (Δ q Cu=0.41 e and Δ q Ag=0.32 e) as well as a formation of partly covalent Me– F s bonds across the interface (Mulliken bond populations p Cu– Fs =0.25 e and p Ag– Fs =0.33 e).