Density functional study of oxygen on Cu(100) and Cu(110) surfaces

Using density-functional theory within the generalized gradient approximation, we investigate the interaction between atomic oxygen and Cu 100 and Cu 110 surfaces. We consider the adsorption of oxygen at various on-surface and subsurface sites of Cu 100 for coverages of 1/8 to 1 monolayers ML . We find that oxygen at a coverage of 1/2 ML preferably binds to Cu 100 in a missing-row surface reconstruction, while oxygen adsorption on the nonreconstructed surface is preferred at 1/4 ML coverage consistent with experimental results. For Cu 110 , we consider oxygen binding to both nonreconstructed and added-row reconstructions at various coverages. For coverages up to 1/2 ML coverage, the most stable configuration is predicted to be a p 2 1 missing-row structure. At higher oxygen exposures, a surface transition to a c 6 2 added strand configuration with 2/3 ML oxygen coverage occurs. Through surface Gibbs free energies, taking into account temperature and oxygen partial pressure, we construct p ,T surface phase diagrams for O/Cu 100 and O/Cu 110 . On both crystal faces, oxygenated surface structures are stable prior to bulk oxidation. We combine our results with equivalent p ,T surface free energy data for the O/Cu 111 surface to predict the morphology of copper nanoparticles in an oxygen environment.