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MO: Fachverband Molekülphysik

MO 2: Theory: Quantum Chemistry and Molecular Dynamics

MO 2.5: Vortrag

Montag, 14. März 2011, 11:30–11:45, MER 02

First-principles GW calculations for the DNA/RNA nucleobases and for molecules of interest for organic photovoltaics — •Carina Faber^1,2, Claudio Attaccalite², Valerio Olevano², Erich Runge¹, and Xavier Blase² — ¹Institut für Physik, Technische Universität Ilmenau, 98693 Ilmenau, Germany, — ²Institut Néel, CNRS and Université Joseph Fourier, BP 166, 38042 Grenoble Cedex 9, France

We evaluate the performance of ab-initio GW calculations for the ionization energies (IEs) and HOMO-LUMO gaps of thirteen molecules of interest for organic photovoltaics. Standard G0W0 calculations significantly improve the IE and the bandgap as compared to DFT Kohn-Sham results, but the calculated quasiparticle values remain too small as a result of overscreening. Starting from HF-like eigenvalues yields much better results with only 2-4% deviation from experiment and is equivalent to performing self-consistency on the eigenvalues. As further test, we study the quasiparticle properties of the DNA/RNA nucleobases. Starting from KS-eigenstates obtained with (semi)local functionals, self-consistency on the eigenvalues allows to obtain IEs and electron affinities within an average 0.1 eV and 0.2 eV error, respectively, with respect to coupled-cluster and multi-configurational perturbative quantum chemistry approaches. GW calculations predict the correct pi-character of the HOMO as result of several level crossings between DFT and GW calculations. Our calculations are based on an efficient Gaussian-basis implementation of GW with explicit treatment of the dynamical screening through contour deformation techniques.