Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 74: Focussed session: Theory and computation of electronic structure: new frontiers VI (jointly with HL, DS)
O 74.1: Vortrag
Donnerstag, 17. März 2011, 15:00–15:15, TRE Phy
Excited States from GW: the role of self-consistency — •Fabio Caruso1, Xinguo Ren1, Patrick Rinke1, Angel Rubio1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut, Faradayweg 4-6, Berlin, Germany — 2Universidad del Pais Vasco, San Sebastian, Spain
The GW approximation offers an accurate framework to study ab-initio electronic excitations in molecules and solids. However, due to its numerical cost, GW is mostly introduced perturbatively following a density-functional theory (DFT) calculation (G0W0). We have implemented a fully self-consistent GW scheme based on the iterative solultion of Dyson’s equation in the all-electron localized basis set code FHI-aims [http://www.fhi-berlin.mpg.de/aims]. The self-consistent treatment corrects several pathologies of the G0W0 scheme, such as the violation of particle number conservation and the dependence on the starting point. Our self-consistent GW total energies are in good agreement with available literature values [Stan et al, JCP 130, 114105 (2009)]. From the GW spectral function we extracted the ionization energies of a set of small molecules. The values are close to experimental results, but exhibit a slight tendency to underestimate. Building on this we apply self-consistent GW to charge-transfer systems. At large separation between the molecular fragments time-dependent DFT in (semi-)local approximations underestimates the charge-transfer energy. This error can be traced back to the wrong description of the HOMO-LUMO gap and its evolution with intermolecular distance. This error is capture by GW as it properly accounts for the difference between the donor ionization potential and acceptor electron affinity.