Adsorption of atomic oxygen on Ag(001): a study based on density-functional theory

We present a theoretical study-based on first principles calculations-aimed at characterizing the surface reconstructions A which occur at the Ag(0 0 1) surface A hen oxygen is dosed on it. We first model this system at different coverages using (1 x 1), c(2 x 2). and p(2 x 2) structures of oxygen atoms adsorbed on the hollow sites of the Ag(0 0 1) surface. The corresponding equilibrium geometries are obtained by accurate energy minimizations performed within density-functional theory in the local density or in the generalized gradient approximations. We then compare the energies of these structures with that of oxygen adsorbed on a (2root2 x root2) missing-row reconstructed substrate. recently proposed to be the stable phase at low temperature on the basis of X-ray photo-electron diffraction experiments. We do find evidence that the surface structure might be stabilized by a missing-row reconstruction. though our predicted geometry differs from that previously proposed. (C) 2002 Elsevier Science B.V. All rights reserved.