Adsorption of atomic oxygen on Ag(0 0 1): a study based on density-functional theory

We present a theoretical study––based on first principles calculations––aimed at characterizing the surface reconstructions which occur at the Ag(0 0 1) surface when oxygen is dosed on it. We first model this system at different coverages using (1×1), c(2×2), and p(2×2) 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 (22×2) 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.