Extra-atomic relaxation energies and the Auger parameter

A simple procedure is used to derive several of the models that have been developed to understand relaxation energies, and especially the relationship between the Auger parameter and the extra-atomic relaxation energy. The approach shows clearly the assumptions that are made in these models and the next level of higher-order terms needed in the evaluation of extra-atomic relaxation energies from the Auger parameter. Numerical evaluation of these higher-order terms shows that they are probably small, except when comparison is made between atoms in very dissimilar environments. The problems that arise when the final orbitals of the Auger transition are not entirely in the core are considered.