Oxygen subsurface adsorption on the Cu(110)-c(6 × 2) surface

To understand the initial steps of the oxidation of Cu(110), we applied density functional theory (DFT) calculations to study oxygen subsurface adsorption at the Cu(110)-c(6 × 2) reconstructed surface by increasing oxygen coverage. A transition from oxygen octahedral occupancy to tetrahedral preference occurs when the coverage reaches 1 monolayer, which may signal the onset of bulk oxidation that initially forms highly distorted CuO tetrahedrons by comparing the bond lengths and angles of the resulting CuO tetrahedron with the bulk Cu2O structure. These results suggest that a critical oxygen coverage is required for such a crossover from the oxygen chemisorption to bulk oxide formation. A comparison with the oxygen subsurface adsorption at Cu(100) suggests that the Cu(110) surface has a larger tendency to form CuO tetrahedrons.