Charge models for electron spectroscopy of disordered alloys

Disorder broadening can be observed in the core photoelectron spectra of metallic alloys. This effect can be simulated using a model in which site charges are assumed to be proportional to number of "unlike" atoms in the nearest-neighbor shell. This linear charge model (LCM) gives a sensible description of the variation in Madelung potential in disordered alloys and is reasonably self-consistent but significantly overestimates core disorder broadening as compared with ab initio core eigenvalue calculations and experimental core-level binding-energy measurements. Two generalizations of the LCM are investigated: an electronegativity model, in which charge is exchanged between unlike nearest neighbors in a nonlinear fashion, and a linear multishell model. Analytical and computational results are presented in each case and the implications for the analysis of core-level photoelectron spectra are discussed.