evGW ionization potentials at G₀W₀ cost

The poles of the single-particle Green’s function correspond to the electron addition and removal energies probed in direct and inverse photoemission experiments, and thus provide a direct link between theory and experiment. One way to extract such energies is to use the GW approximation to the self-energy, a popular method in electronic structure theory. Like other nonlinear methods, the GW quasiparticle equations should be solved self-consistently, however, comparatively few fully self-consistent (scGW) solutions have been performed throughout the years due to their high computational cost. Non-self-consistent alternatives, like the one-shot G₀W₀ demand less computational resources but depend on the mean-field orbitals and energies that are used as input. Furthermore, G₀W₀ energies are not good starting points to obtain accurate neutral excitations using the Bethe-Salpeter Equation (BSE) formalism in finite systems. The simplest way to incorporate more physics is to iterate the eigenvalues (evGW) until they remain self-consistent, an effort that comes at a higher computational cost. In this talk, we will show that including an approximation to the derivative discontinuity (DD) of the nearly correct asymptotic potential (NCAP) exchange-correlation functional yields G₀W₀@NCAP-DD quasiparticle energies comparable to the more expensive evGW@GGA energies.