Ab initio study of the optical response of Cu(0Â 0Â 1) surface

We present ab initio density functional calculation of the optical properties of Cu(0 0 1) surface, carried out using interband transitions based on energy bands calculated through ab initio self-consistent method of linear muffin tin orbitals (LMTO). The imaginary part of the dielectric function ϵ2(ω) exhibits three dominant peaks and two small shoulder-like structures. Three of them, located at 0.53 eV, 2.73 and 3.39 eV, are obtained for a light polarized parallel to the Cu(0 0 1) surface whereas the two others, at 1.70 and 2.73 eV, are due to photons polarized in the direction perpendicular to the surface. We show that not all the peaks have their origin in interband transitions involving localized states, but also in electronic transitions between parallel energy bands. All these transitions are identified by their orbital symmetries and by the atomic sites involved in the process.