Regensburg 2022 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 41: Organic Semiconductors 2

HL 41.1: Vortrag

Freitag, 9. September 2022, 09:30–09:45, H34

Understanding structure-to-property relationships for phonons and thermal transport in hydrogen-bonded organic semiconductors. — •Lukas Legenstein, Lukas Reicht, Tomas Kamencek, Sandro Wieser, and Egbert Zojer — Institute of Solid State Physics, Graz University of Technology, Graz, Austria

Research on organic semiconductors (OSC) has primarily focused on their (opto-)electronic properties. The understanding of phonons in these materials is, however, still rather poorly developed, despite their crucial role for charge and heat transport processes. Of central importance in this context are lattice phonons dominated by translations and rotations of entire molecules, which are coupled through non-covalent interactions. To elucidate how non-covalent bonding types such as H-bonding and π-π interactions affect phonons in otherwise vdW-stacked OSCs, we simulate the phonon bands of crystalline quinacridone (QA), as a prototypical H-bonded OSC. Notably, QA forms polymorphs with fundamentally different crystal structures, which strongly impact the observed phonons. The obtained phonon bands show complex dispersions with avoided crossings and mode hybridisations due to a mixing of inter- and intra-molecular vibrations. The phonons are simulated combing the phonopy package with density-functional theory employing the FHI-aims and VASP codes. The calculated phonon band structures are also used for benchmarking on-the-fly trained machine learning force fields calculated with VASP, which are then employed for modelling thermal transport within the Green-Kubo formalism.