SKM 2021 – wissenschaftliches Programm
CPP 6.16: Poster
Dienstag, 28. September 2021, 17:30–19:30, P
Ground- and excited-state properties of tetraphenyl compounds from first-principles calculations — •Kevin Eberheim, Christof Dues, and Simone Sanna — Institut für Theoretische Physik and Center for Materials Research, Justus-Liebig-Universität Gießen, 35392 Gießen, Germany
Tetraphenyl compounds with formula X(C6H5)4 (X being a tetravalent atom of the 14th group such as C, Si, Ge, Sn, Pb), crystallize either in a tetragonal crystalline structure or in an amorph phase . Depending on their habitus, the compounds are characterized by very different optical properties. The molecular crystals are known for their second harmonic generation (SHG) properties, while the amorph phase is a white light emitter. Tetraphenyl molecules feature indeed the delocalized π-orbitals, which have been proposed as a prerequisite for the white-light generation . In an attempt to understand the mechanisms related to the white light emission, we model the structural, electronic and vibrational properties of different X(C6H5)4 structures within density functional theory. The calculated structural parameters closely reproduce the measured values, however vdW corrections are crucial for a correct description of the structural properties. This confirms that dispersion forces are responsible for the intermolecular bonds in the compound. Different implementations of the vdW forces lead to very similar results. Calculated vibrational properties are in agreement with measured Raman spectra.  A Kitaigorodsky, Molecular crystals and Molecules, Acad. Press (1973).  Nils W. Rosemann et al., J. Am. Chem. Soc. 138, 16224 (2016), Science 352, 1301 (2016).