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MO: Fachverband Molekülphysik

MO 14: Theory of Coupled Systems

MO 14.2: Vortrag

Donnerstag, 9. März 2017, 11:15–11:30, N 25

Electron-phonon coupling with DFT — •Oliver Stauffert — Physikalisches Institut, Universität Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg

We describe electronic structures for organic molecules, which are interesting for current research on organic solar cells, with time dependent density functional theory (DFT). Hereby we are especially interested in coupling of nuclear and electronic degrees of freedom. The most widely known occurrence of this coupling can be seen in the vibrational substructure of electronic spectra. These vibrational lines are described by the Franc Condon factors and can be calculated in a DFT framework. Results of simulations for polycyclic aromatic hydrocarbon show excellent agreements with the experimental data. We further investigate the influences of the environment, like a rare gas matrix and additional molecules on the vibrational degrees of freedom.
Another consequence of electron phonon coupling can be seen in phonon assisted electron hopping. Conduction in organic systems is often described by electronic hopping in terms of a Hubbard Hamiltonian. The hopping parameter hereby depends on the distance of next neighbor atoms. Vibrations along the atomic axis can change the distance accordingly and enhance electronic hopping. This can lead to interesting new effects that we are investigating with DFT and an Su-Schrieffer-Heeger [1] model.

[1] W.P. Su, J.R. Schrieffer, and A.J. Heeger, Phys. Rev. Lett. 42, 1698 (1979)