Quasiparticle and fully self-consistent GW methods: an unbiased analysis using Gaussian orbitals

TL;DR

This study compares various GW approximation schemes using Gaussian orbitals, revealing that fully self-consistent GW performs best for molecules, while all schemes are similar for solids, emphasizing the importance of implementation details.

Contribution

It provides an unbiased, comprehensive comparison of GW methods with consistent formalism and implementation, clarifying their relative performances for different systems.

Findings

Full self-consistent GW outperforms other schemes for molecules.

Different self-consistency schemes perform similarly for solids.

Implementation details significantly affect GW method performance.

Abstract

We present a comparison of various approximations to self-consistency in the GW method, including the one-shot G0W0 method, different quasiparticle self-consistency schemes, and the fully self-consistent GW (scGW) approach. To ensure an unbiased and equitable comparison, we have implemented all the schemes with the same underlying Matsubara formalism, while employing Gaussian orbitals to describe the system. Aiming to assess and compare different GW schemes, we analyze band gaps in semiconductors and insulators, as well as ionization potentials in molecules. Our findings reveal that for solids, the different self-consistency schemes perform very similarly. However, for molecules, full self-consistency outperforms all other approximations, i.e., the one-shot and quasiparticle self-consistency GW schemes. Our work highlights the importance of implementation details when comparing different GW methods. By employing state-of-the-art fully self-consistent, finite temperature GW calculations, we have successfully addressed discrepancies in the existing literature regarding its performance. Our results also indicate that when stringent thresholds are imposed, the scGW method consistently yields accurate results.