Core level shifts at bcc transition metal surfaces deduced from the calculation of surface segregation energies

Abstract

Within the equivalent core approximation, the core level shift between surface and bulk atoms is equal to the surface segregation energy of an impurity of atomic number Z + 1 in a matrix of atomic number Z. These energies have never been calculated systematically but have been deduced from thermodynamical data using additional approximations. We present here a tight-binding study of these segregation energies and compare them with previous approaches to the calculation of surface core level shifts. The agreement between theory and experiments is significantly improved.