Total Energies from GW Calculations

The possibilities of obtaining accurate total energies from GW calculations at various levels of self-consistency are investigated. In the conserving approximation known as the fully self-consistent GW approach there is no ambiguity in calculating the total energy, and the results for the electron gas compare well with those of accurate Monte Carlo calculations. We demonstrate how to obtain chemical potentials and total energies of similar accuracy from partially self-consistent ( GW₀) calculations.