Improved One-Shot Total Energies from the Linearized GW Density Matrix.

The linearized GW density matrix (γ) is an efficient method to improve the static portion of the self-energy compared to that of ordinary perturbative GW while keeping the single-shot simplicity of the calculation. Previous work has shown that γ gives an improved Fock operator and total energy components that approach the self-consistent GW quality. Here, we test γ for dimer dissociation for the first time by studying N, LiH, and Be. We also calculate a set of self-consistent GW results in identical basis sets for a direct and consistent comparison. γ approaches self-consistent GW total energies for a starting point based on a high amount of exact exchange. We also compare the accuracy of different total energy functionals, which differ when evaluated with a non-self-consistent density or density matrix. While the errors in total energies among different functionals and starting points are small, the individual energy components show noticeable errors when compared to reference data. The energy component errors of γ are smaller than functionals of the density and we suggest that the linearized GW density matrix is a route to improving total energy evaluations in the adiabatic connection framework.