Analysis of Auger-parameter and XPS shifts: Application of potential models

The use of free-atom-to-metal Auger-parameter shifts to determine atomic-potential parameters for Na, Mg, and Zn is shown to lead to an apparent inconsistency between the effects of perfect screening and the influence of valence-wave-function compression in the metallic state. This conflict is traced to the neglect in standard potential models of the quadratic dependence of the atomic-core potential on valence charge. We propose a generalized model which gives a good description of the atomic-core potential, and show that this can be used to derive empirical solid-state potential parameters from metal-atom Auger-parameter shifts.