Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 106: Frontiers of Electronic Structure Theory: Many-Body Effects, Methods (organized by O)

TT 106.12: Vortrag

Donnerstag, 19. März 2015, 18:00–18:15, MA 004

Quasiparticle Self-Consistent GW for Molecules — •Ferdnand Kaplan^1,2,3, Michiel van Setten^1,2,5, Florian Weigend^1,3, and Ferdinand Evers^1,2,3,4 — 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.