Core-cancellation functions for evaluating exchange-correlation functionals in first-principles pseudopotential calculations

Within the framework of density-functional theory, first-principles pseudopotential methods have been highly successful in modeling the valence-electron properties of solids in their ground states. In this paper, we introduce ``core-cancellation functions'' which are designed to improve the accuracy of the treatment of the exchange-correlation interaction. This formalism, expected to be especially effective for transition metals, is tested for bulk tungsten and niobium, comparing results obtained using the local-density approximation to those obtained using the generalized gradient approximation.