Surface core-level shift of Pd at the AgcPd1−c(1 1 1) surface: Nonlinear subsurface effects

The surface core-level binding-energy shift (SCLS) of Pd at the AgcPd1−c(1 1 1) surface is calculated as a function of bulk concentration of the alloy. The equilibrium volume and the surface concentration profile used in the calculations refer to the 0 K case. The SCLSs are evaluated within the Z + 1 approximation. The results are analysed using the mixing enthalpy of the alloy and the bulk and surface chemical potentials. A relation of the SCLS to the bulk concentration is considered. This relation is shown to be mediated by the surface concentration profile which induces the observed nonlinear behaviour. The results are interpreted using a simple model for the alloy electronic structure.