Electronic Free-Energy beyond the GW Approximation

Abstract

We propose a scheme based on a kind of self-consistent perturbation theory, where both the one-particle Green's function and the screened Coulomb interaction are determined self-consistently. To describe the screened Coulomb interaction dynamics, we use a functional-integral representation of the free energy. Our main approximation is to replace the exact free energy functional by a variationally chosen quadratic form in the fluctuating field. This procedure leads to the inclusion of electron correlation beyond the GW approximation. As an illustration, the scheme is used to calculate the potential surface of hydrogen fluoride molecule.