title: Off-Diagonal Self-Energy Terms and Partially Self-Consistency in GW Calculations for Single Molecules: Efficient Implementation and Quantitative Effects on Ionization Potentials.
abstract: The GW method in its most widespread variant takes, as an input, Kohn-Sham (KS) single particle energies and single particle states and yields results for the single-particle excitation energies that are significantly improved over the bare KS estimates. Fundamental shortcomings of density functional theory (DFT) when applied to excitation energies as well as artifacts introduced by approximate exchange-correlation (XC) functionals are thus reduced. At its heart lies the quasi-particle (qp) equation, whose solution yields the corrected excitation energies and qp-wave functions. We propose an efficient approximation scheme to treat this equation based on second-order perturbation theory and self-consistent iteration schemes. We thus avoid solving (large) eigenvalue problems at the expense of a residual error that is comparable to the intrinsic uncertainty of the GW truncation scheme and is, in this sense, insignificant.
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology , Campus North, D-76344 Karlsruhe, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Kaplan
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology , Campus North, D-76344 Karlsruhe, Germany.|Institute of Physical Chemistry, Karlsruhe Institute of Technology , Campus South, D-76021 Karlsruhe, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Weigend
authors.affiliation: Institute of Theoretical Physics, University of Regensburg , D-93040 Regensburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Evers
authors.affiliation: Nanoscopic Physics, Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain , Chemin des Étoiles 8, bte L7.03.01, 1348 Louvain-la-Neuve, Belgium.
authors.forename: M J
authors.initials: MJ
authors.lastname: van Setten