The GW Miracle in Many-Body Perturbation Theory for the Ionization Potential of Molecules

• Published in: Frontiers in chemistry 2021-12, Vol.9, p.749779-749779
• Main Authors: Bruneval, Fabien, Dattani, Nike, van Setten, Michiel J
• Format: Article
• Language: English
• Subjects: Chemistry; density-functional theory (DFT); electronic structure ab initio calculations; feynman diagram expansion; Green’s function (GF); ionization potential (IP); many-body ab initio structure
• ISSN: 2296-2646; 2296-2646
• DOI: 10.3389/fchem.2021.749779

We use the GW100 benchmark set to systematically judge the quality of several perturbation theories against high-level quantum chemistry methods. First of all, we revisit the reference CCSD(T) ionization potentials for this popular benchmark set and establish a revised set of CCSD(T) results. Then, for all of these 100 molecules, we calculate the HOMO energy within second and third-order perturbation theory (PT2 and PT3), and, as post-Hartree-Fock methods. We found to be the most accurate of these three approximations for the ionization potential, by far. Going beyond by adding more diagrams is a tedious and dangerous activity: We tried to complement with second-order exchange (SOX), with second-order screened exchange (SOSEX), with interacting electron-hole pairs ( ), and with a density-matrix ( ). Only the result has a positive impact. Finally using an improved hybrid functional for the non-interacting Green's function, considering it as a cheap way to approximate self-consistency, the accuracy of the simplest approximation improves even more. We conclude that is a miracle: Its subtle balance makes both accurate and fast.