Relationship between electronic and geometric structures of the O/Cu(001) system

The electronic structure of the (22×2)R45° O/Cu(001) system has been calculated using locally self-consistent, real space multiple scattering technique based on first principles. Oxygen atoms are found to perturb differentially the long-range Madelung potentials, and hence the local electronic subbands at neighboring Cu sites. As a result the hybridization of the oxygen electronic states with those of its neighbors leads to bonding of varying ionic and covalent mix. Comparison of results with those for the c(2×2) overlayer shows that the perturbation is much stronger and the Coulomb lattice energy much higher for it than for the (22×2)R45° phase. The main driving force for the 0.5 ML oxygen surface structure formation on Cu(001) is thus the long-range Coulomb interaction which also controls the charge transfer and chemical binding in the system.