Reproducibility in $G_0W_0$ calculations for solids

• Published in: Computer physics communications Vol. 255
• Main Authors: Rangel, Tonatiuh, del Ben, Mauro, Varsano, Daniele, Antonius, Gabriel, Bruneval, Fabien, da Jornada, Felipe H., van Setten, Michiel J., Orhan, Okan K., O'Regan, David D., Canning, Andrew, Ferretti, Andrea, Marini, Andrea, Rignanese, Gian-Marco, Deslippe, Jack, Louie, Steven G., Neaton, Jeffrey B.
• Format: Journal Article
• Language: English
• Published: Elsevier 2020
• Subjects: Computational Physics; Condensed Matter; Materials Science; Physics
• ISSN: 0010-4655; 1879-2944
• DOI: 10.1016/j.cpc.2020.107242

Ab initio many-body perturbation theory within the GW approximation is a Green’s functionformalism widely used in the calculation of quasiparticle excitation energies of solids. In whathas become an increasingly standard approach, Kohn-Sham eigenenergies, generated from a DFTcalculation with a strategically-chosen exchange correlation functional “starting point”, are usedto construct G and W , and then perturbatively corrected by the resultant GW self-energy. Inpractice, there are several ways to construct the GW self-energy, and these can lead to variationsin predicted quasiparticle energies. For example, for ZnO and TiO 2 , reported GW fundamentalgaps can vary by more than 1 eV. In this work, we address the convergence and key approximationsin contemporary G 0 W 0 calculations, including frequency-integration schemes and the treatment ofthe Coulomb divergence in the exact-exchange term. We study several systems, and compare threedifferent GW codes: BerkeleyGW, Abinit and Yambo. We demonstrate, for the first time, thatthe same quasiparticle energies for systems in the condensed phase can be obtained with differentcodes, and we provide a comprehensive assessment of implementations of the GW approximation.