Self-consistent GW: All-electron implementation with localized basis functions

Abstract

This paper describes an all-electron implementation of the self-consistent GW (sc-GW) approach -- i.e. based on the solution of the Dyson equation -- in an all-electron numeric atom-centered orbital (NAO) basis set. We cast Hedin's equations into a matrix form that is suitable for numerical calculations by means of i) the resolution of identity technique to handle 4-center integrals; and ii) a basis representation for the imaginary-frequency dependence of dynamical operators. In contrast to perturbative G0W0, sc-GW provides a consistent framework for ground- and excited-state properties and facilitates an unbiased assessment of the GW approximation. For excited-states, we benchmark sc-GW for five molecules relevant for organic photovoltaic applications: thiophene, benzothiazole, 1,2,5-thiadiazole, naphthalene, and tetrathiafulvalene. At self-consistency, the quasi-particle energies are found to be in good agreement with experiment and, on average, more accurate than G0W0 based on Hartree-Fock (HF) or density-functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional. Based on the Galitskii-Migdal total energy, structural properties are investigated for a set of diatomic molecules. For binding energies, bond lengths, and vibrational frequencies sc-GW and G0W0 achieve a comparable performance, which is, however, not as good as that of exact-exchange plus correlation in the random-phase approximation (EX+cRPA) and its advancement to renormalized second-order perturbation theory (rPT2). Finally, the improved description of dipole moments for a small set of diatomic molecules demonstrates the quality of the sc-GW ground state density.