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Abstract

The locally self-consistent real-space multiple-scattering technique has been applied to calculate the electronic structure and chemical binding for the c(2x2) O overlayer on Cu(001), for a set of values of d(O-Cu1), the height of O above the fourfold hollow sites, as proposed from experiment. The O-Cu bond is found to have a mixed ionic-covalent character in all cases. However, the electron charge transfer from the metal surface to O depends strongly on d(O-Cu1) and is traced to the strength of the long-range Coulomb interaction. A competition between the hybridization of Cu-d(xz) states with O-p(x)/p(y) states and that of Cu-d(x 2-y 2) states with O-p(z) states, is shown to control the modification of the electronic structure as O atoms approach the Cu(001) surface. Further, the O valence electronic charge density is found to be anisotropic and nonmonotonically dependent on d(O-Cu1). We compare the electronic structure of the c(2x2) O overlayer on Cu(001) and Ni(001), to draw conclusions about their relative stability.