GENERALIZED FRIEDEL SUM FROM LLOYD FORMULA

Expressions for the generalized Friedel sum rule are derived which are applicable as a condition for charge neutrality at defects in metalli c systems. These defects include the thoroughly studied substitutional impurity as well as the poorly explored interstitial impurity and an atom at the saddle-point position between two vacancies, being typical for substitutional electromigration. The expressions are derived star ting from Lloyd's formula for the density of states of an arbitrary co llection of scattering potentials.