Oxygen adsorption on the Ag(111) surface: a quantum chemical study by the NDDO/MC method

The forms of the atomic oxygen adsorbed on the Ag(lll) face were investigat ed using the semi-empirical NDDO/MC method within the modified cluster appr oximation. Two oxygen positions - surface (over the octahedral hollow) and the subsurface (in the hollow) one - between the first two layers of (111) face were studied. A cross-section of the potential energy for the oxygen p enetration into subsurface positions has been computed. A new approach was applied to take into account the lattice relaxation caused by the interacti on with adsorbate. The doubly-excited-CI-like correlation corrections to th e diffusion and desorption barriers were estimated. The barrier of the oxyg en atom diffusion through the surface was shown to be substantially lower t han that of the desorption. (C) 2000 Elsevier Science B.V. All rights reser ved.