Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 91: Frontiers of electronic structure theory: Many-body effects, methods
HL 91.12: Talk
Thursday, March 19, 2015, 18:00–18:15, MA 004
Quasiparticle Self-Consistent GW for Molecules — •Ferdnand Kaplan1,2,3, Michiel van Setten1,2,5, Florian Weigend1,3, and Ferdinand Evers1,2,3,4 — 1Institute of Nanotechnology (INT) — 2Institute for Theoretical Condensed Matter Physics (TKM) — 3Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany — 4Universität Regensburg, D-93040 Regensburg, Germany — 5Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
One of the most used approaches for the computational study of nanoscale systems and molecules is the density functional theory (DFT). However, DFT calculations of single particle excitation spectra, e.g. ionization potentials, often suffer from method-inherent difficulties. To systematically improve the estimation of quasi-particle energies for molecular system, we have implemented the GW method. The approach represents a perturbative expansion of the many-body Green’s function with respect to the screened Coulomb interaction, W.
On G0W0 level the GW-self energy is calculated with the Kohn-Sham Green’s function of the underlying DFT. Hence, one finds a strong dependence of the excitation energies on the reference system, i.e. DFT functionals. To overcome this problem, we implemented a self-consistent cycle which takes into account the deviations of the quasiparicle(qp)-wavefunctions from their Kohn-Sham parents.
We find that this procedure converges to a fixed point solution which is independent of the reference system. For the testset of molecules anlyzed by us so far, the results for ionization-energy and electron-affinity improve upon G0W0, when comparing to experimental data.