Berlin 2014 – scientific programme

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MO: Fachverband Molekülphysik

MO 4: Theory 1: Molecular Dynamics

MO 4.5: Talk

Monday, March 17, 2014, 15:15–15:30, BEBEL SR144

A New Efficient Method for Calculation of Frenkel Exciton Parameters in Molecular Aggregates — •Per-Arno Plötz¹, Thomas Niehaus², and Oliver Kühn¹ — ¹Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — ²Institut I - Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany

The Frenkel exciton Hamiltonian models an aggregate as Coulomb-coupled monomers. In addition to the monomeric excitation energies the Coulomb coupling is an essential parameter for its description. It is shown that this coupling can be very efficiently calculated using time-dependent tight-binding based density functional theory (TD-DFTB), which offers a consistent way to describe the electronic structures of the monomers and the exciton coupling in the aggregate. Coulomb couplings are expressed in terms of self-consistently determined Mulliken transition charges, obtained in a sub-system-like formulation. This opens the possibility for a consistent on-the-fly determination of Frenkel exciton parameters in molecular dynamics simulations.

The performance of the method is studied by comparing to DFT-based calculations for a small test system of a formaldehyde oxime dimer. Applied to a perylene bisimide dimer it offers the possibility to explore the dependence of the Coulomb coupling on the intermolecular coordinates. This yields an interpretation of the observed biphasic aggregation (F. Fennel et al., JACS 2013, doi:10.1021/ja409597x).