Adsorption and diffusion of O atoms on metallic (1 0 0) surfaces. Cluster and periodic slab approaches

Abstract

A computational study of adsorption and diffusion of oxygen atoms on (1 0 0) surfaces of Au, Cu, Ag, and Pt was performed by means of density functional theory (DFT) calculations. Two different methodologies were employed, namely the cluster model and the periodic slab model. The adsorption distances and energies of the atoms on top, hollow, and bridge sites of the (1 0 0) surfaces were calculated in order to elucidate preferential adsorption sites for oxygen on each metal. Diffusion of the O atom from the most stable adsorption site to the nearest neighbouring one was studied to obtain activation energy and diffusion velocity values. Adsorption energies in the presence of nearest neighbors were also calculated. In most cases the structural results obtained from the cluster model and periodic slab qualitatively show the same trends, but the energies differ. In general, adsorption energies (in terms of their absolute values) and diffusion rates are higher with the slab model. Both models agree in showing higher values on Cu. The preferential adsorption sites are hollow for O/Cu(1 0 0) and O/Ag(1 0 0), and bridge for O/Pt(1 0 0). For the O/Au(1 0 0) system the preferential adsorption sites are hollow and bridge with the cluster and slab model respectively.