QSGW: Quasiparticle Self consistent GW with ladder diagrams in W

Abstract

We present an approach to calculate the electronic structure for a range of materials using the quasiparticle self-consistent GW method with vertex corrections included in the screened Coulomb interaction W. This is achieved by solving the Bethe-Salpeter equation for the polarization matrix at all k-points in the Brillouin zone. We refer to this method as QSGW^. We show that including ladder diagrams in W can greatly reduce the band gap overestimation of RPA-based QSGW. The resultant discrepency of the calculated band gap in this method is then attributed mostly to the fact that electron-phonon contributions to W are neglected; which would allow one to then obtain an estimate for the size of this effect. We present results for a range of systems from simple sp semiconductors to the strongly correlated systems NiO and CoO. Results for systems where the RPA-based QSGW band gap is larger than expected are investigated, and an estimate for the Frolich contribution to the gap is included in a few polar compounds where QSGW can overestimate the gap by as much as 2 eV. The improvement over QSGW for the dielectric constants is also presented