Abstract
We combine polarization-resolved low-frequency Raman microscopy and dispersion-corrected density-functional calculations (DFT-D3) to study polymorph-dependent lattice vibrations in coronene, a model molecular system for nanographenes and disklike organic semiconductors that exhibits two crystalline structures with distinct electronic and optical properties. Changes in low-energy Raman-active lattice phonons are followed across the γ- to β-phase transition at 150 K. Raman frequencies calculated using DFT-D3 agree to within 4 cm-1, and on the basis of polarization dependence of peak positions and intensities we achieve a clear mode assignment. Studies of the associated atomic motions show how the pure librational and rotational modes of γ-coronene change into mixed roto-librations in the β-phase, explaining the remarkable differences in Raman spectra of the two phases.
Original language | English |
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Article number | 125601 |
Journal | Physical Review Materials |
Volume | 3 |
Issue number | 12 |
DOIs | |
Publication status | Published - 6 Dec 2019 |
Funding
We are grateful to Wendy Lambson for technical support. J.S. is grateful to the University of Manchester for the award of a Presidential Fellowship. N.B. acknowledges funding and support from the Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training in Condensed Matter Physics (CDT-CMP), Grant No. EP/L015544/1. This research made use of the Balena High Performance Computing (HPC) Service at the University of Bath. X-ray diffraction facilties were provided through the Chemical Characterisation and Analysis Facility (CCAF) at the University of Bath.
ASJC Scopus subject areas
- General Materials Science
- Physics and Astronomy (miscellaneous)
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Dual source (Cu and Mo) Single Crystal Diffractometer (SuperNova)
Material and Chemical Characterisation (MC2)Facility/equipment: Equipment
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Raman confocal microscope RENISHAM INVIA
Material and Chemical Characterisation (MC2)Facility/equipment: Equipment