Electronic couplings in molecular crystals: Tight-Binding fits vs. cluster-based approaches
Florian Mayer
11:15 - 12:15 Wednesday 23 January 2019 PH01150 The ever-growing interest in electronic properties of new materials
triggers the development of new methodologies for their reliable de-
scription. For modelling charge-transport properties, theories span the
full range from band transport via dynamic-disorder models to hop-
ping approaches. For all these methods the electronic coupling be-
tween neighboring molecules is a crucial input. This quantity can be
calculated with various approaches most of them relying on simula-
tions on molecular dimers and small clusters. In contrast, the fitting
of extended Tight-Binding models to full band structures allow the
evaluation of inter-molecular coupling, treating the molecules in their
actual crystalline environments. In the present contribution, for the
prototypical examples of pentacene and quinacridone, applying the
above-mentioned complementary approaches, issues like
next-nearest neighbor coupling, interference between different coupling
directions for coherent transport, and how to deal with off-Gamma
point band extrema are discussed. For non-periodic calculations also a
new variant of the fragment orbital and electronic splitting method is presented.
The obtained results provide insight into the strengths and limitations
of the various approaches and help to better understand electronic
coupling in organic semiconductors.
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Institute of Solid State Physics
