Valence electron binding energies of molecules may be calculated efficiently with electron-propagator methods that employ the diagonal self-energy, or quasiparticle, approximation in the canonical Hartree-Fock orbital basis. Alternatives to diagonal self-energies that are complete through second or third order (i.e., D2 and D3) in the fluctuation potential typically include renormalizations that incorporate certain classes of higher-order terms. Whereas approximate schemes such as the outer valence Green functions (OVGF) or the renormalized partial third order method (P3+) require evaluation only of terms in second or third order, explicit renormalizations such as G0W0 and the nondiagonal, renormalized, second-order method (NR2) require iterative algorithms in the determination of higher-order corrections. These well-known methods are compared with a new generation of approximately and explicitly renormalized self-energies with comparable computational demands but higher levels of accuracy. In addition, the effects of adding exchange terms in G0W0 calculations and of neglecting same-spin contributions in the D2 self-energy are assessed. To reveal the intrinsic properties of the self-energy approximations, basis-set saturation has been achieved. The latter results provide support for extrapolation schemes and the identification of self-energy and basis-set combinations with optimal predictive capabilities.

Efficient prediction of electron binding energies with quasiparticle self-energies: From finite-order to GW to renormalized electron-propagator methods

ACS Fall 2021

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