Density functional theory studies on stress stabilization of the Cu(1 1 0) striped phase

Under oxygen exposure, the Cu(1 1 0) surface shows a striped phase consisting of alternating bare (1 1 0) surface areas and added-row (2 × 1)O reconstructions. Density functional theory is used to show that the major origin for the formation of the striped phase is the elastic interaction between these areas. The difference between the surface stress of the bare surface and the (2 × 1)O covered surface is predicted to be 1.3 N/m in reasonable agreement with values derived from grazing incidence X-ray diffraction. Supercell calculations for periods of up to 62 إ confirm that the formation of the striped phase is favorable compared to an added-row (4 × 1)O reconstruction with the same coverage. But the predicted equilibrium period of roughly 30 إ is significantly smaller than in experiment. The calculations are impeded by the surface energy alternating with the number of layers in the slab. This behavior is related to a quantum well behavior of the Cu 4s-electrons. A simple model for this behavior is discussed and compared to ab initio results.