Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 21: Electronic Structure and Spin-Orbit Interaction I

O 21.3: Talk

Monday, March 11, 2013, 16:30–16:45, H42

Double excitations from modified Hartree-Fock equations — •Iris Theophilou¹, Maria Tassi², and Stavros Thanos² — ¹Peter Grünberg Institut (PGI) and Institute for Advanced Simulation (IAS) Forschungszentrum Jülich D-52425 Jülich, Germany — ²Institute of Material Science, National Center for Scientific Research Demokritos, 15310, Athens, Greece

While doubly excited states have become important in technological applications, e.g. in increasing the efficiency of solar cells, their description using ab initio methods is a great theoretical challenge because double excitations cannot be described in linear response based on a single Slater determinant. We recently developed a modified Hartree-Fock (HF) approximation for calculating singly excited states [1]. In the present work we extend this method further to also allow for the description of doubly excited states. We describe the double excitation as two holes in the subspace spanned from the occupied HF orbitals and two particles in the subspace of virtual HF orbitals. A subsequent minimization of the energy optimizes the representation of both the holes and the particles in the occupied and virtual subspaces, respectively. We test our method for various atoms and polyene molecules which are known to have excitations with significant double excitation character.

[1] M.Tassi., I.Theophilou, and S.Thanos, Int. J. Quantum Chem. 2012 DOI:10.1002/qua.24049