Renormalized Singles Green’s Function in the T-Matrix Approximation for Accurate Quasiparticle Energy Calculation

Abstract

We combine the renormalized singles (RS) Green's function with the T-matrix approximation for the single-particle Green's function to compute quasiparticle energies for valence and core states of molecular systems. The <i>G</i>_RS<i>T</i>₀ method uses the RS Green's function that incorporates singles contributions as the initial Green's function. The <i>G</i>_RS<i>T</i>_RS method further calculates the generalized effective interaction with the RS Green's function by using RS eigenvalues in the T-matrix calculation through the particle-particle random phase approximation. The <i>G</i>_RS<i>T</i>_RS method provides significant improvements over one-shot methods <i>G</i>₀<i>T</i>₀ and <i>G</i>₀<i>W</i>₀ as demonstrated in calculations for GW100 and CORE65 test sets. It also systematically eliminates the dependence of <i>G</i>₀<i>T</i>₀ on the choice of density functional approximations. For valence states, the <i>G</i>_RS<i>T</i>_RS method provides excellent accuracy, which is better than that of <i>G</i>₀<i>T</i>₀ and <i>G</i>₀<i>W</i>₀. For core states, the <i>G</i>_RS<i>T</i>_RS method identifies correct peaks in the spectral function and significantly outperforms <i>G</i>₀<i>T</i>₀ on core-level binding energies (CLBEs) and relative CLBEs.