Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 47: Frontiers of Electronic Structure Theory: Many-Body Effects on the Nano-Scale III
O 47.10: Talk
Wednesday, March 18, 2015, 13:00–13:15, MA 004
A GW algorithm of reduced complexity for organic crystals — •Saber Gueddida1, Dietrich Foerster1, Peter Koval2, and Daniel Sanchez-Portal2 — 1Laboratoire Ondes et Matière d'Aquitaine, University of Bordeaux, France — 2Donostia International Physics Center, San Sebastian, Spain
Density functional theory (DFT) provides a variational estimate of the electronic structure and geometry of many materials in their ground state. By its construction, DFT is unsuited for a description of the excited states, and particularly so for semi conductors. For these, one resorts to Hedin's GW approximation that gives rather good bands and gaps. A practical limitation of this approach is its computational cost that increases with the fourth power (N**4) of the number of atoms N per unit cell. Starting in 2007 [1], we have developed methods of "reduced complexity" that lower the growth of CPU time in calculations of electronic structure from N**4 to N**3, both for optical absorption [2] and in the GW approximation for finite systems [3]. Here we report on the extension of our methods to crystals, where we reduce the growth of CPU time again from N**4 to N**3, with N now the number of atoms in the unit cell of the crystal. Our work is motivated by organic semiconductors that have too many atoms in their unit cell for O(N**4) algorithms to be practical. Our results should help to improve and optimize organic solar cells. [1] D. Foerster, J. Chem. Phys. 128 (34108) 2008. [2] P. Koval, D. Foerster and O. Coulaud, J. Chem. Theory Comp. 6 (2654) 2010 . [3] D. Foerster, P. Koval, and D. Sánchez-Portal, J. Chem. Phys. 135, 74105 (2011) .