Orthogonalized Plane Wave Method and Total Energy of a Metal

Abstract

We analyze a method for the computation of the total energy of a metal, proposed by Harrison and based upon the following approximations: (a) the self-consistent potential, (b) a second-order perturbation expansion, with a pseudopotential derived from the orthogonalized-plane-wave method. It is shown that the total energy can always be expressed as a sum of terms, each of them being a simple generalization of terms already known from more elementary calculations. The main effect of orthogonalizing the conduction electrons to the core is in increasing the ionic charge. These results are shown for two forms of the total energy. The first one is suitable for computations on the reciprocal lattice and contains a self-energy term, an Ewald's electrostatic term, and a second-order perturbation term; in the second one, a short-range pair interaction between ions is exhibited, the form of which is explicitly given.