Phonon Dispersion in an α‐Perylene d<sub>12</sub>‐Crystal at 10 K

Schleifer, J.; Kalus, J.; Schmelzer, U.; Eckold, G.

doi:10.1002/pssb.2221540114

Cited by 4 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Time-resolved optical reflectivity measurements showed two different strain waves propagating at different speeds, 955 and 4460 m/s (see the Supporting Information). The observed values match the speed of sound of the corresponding transverse acoustic (TA) and longitudinal acoustic (LA) modes in single crystals …”

Section: Resultssupporting

confidence: 64%

“…The observed values match the speed of sound of the corresponding transverse acoustic (TA) and longitudinal acoustic (LA) modes in single crystals. 25…”

Section: Resultsmentioning

confidence: 99%

“…The observed values match the speed of sound of the corresponding transverse acoustic (TA) and longitudinal acoustic (LA) modes in single crystals. 25 Time-resolved GIXD measurements were carried out at the optical pump/X-ray probe setup beamline ID09b at the European Synchrotron Radiation Facility (ESRF). 26 Thin-film samples of 3 × 3 mm 2 size were excited by Ti:sapphire laser pulses of 390 nm wavelength and approximately 100 fs pulse length with angles of incidence of 10°[case (i)] as well as 90°[ case (ii)] with respect to the film surface.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Tuning and Tracking of Coherent Shear Waves in Molecular Films

Lemke¹,

Breiby

Ejdrup³

et al. 2018

ACS Omega

View full text Add to dashboard Cite

We have determined the time-dependent displacement fields in molecular sub-micrometer thin films as response to femtosecond and picosecond laser pulse heating by time-resolved X-ray diffraction. This method allows a direct absolute determination of the molecular displacements induced by electron–phonon interactions, which are crucial for, for example, charge transport in organic electronic devices. We demonstrate that two different modes of coherent shear motion can be photoexcited in a thin film of organic molecules by careful tuning of the laser penetration depth relative to the thickness of the film. The measured response of the organic film to impulse heating is explained by a thermoelastic model and reveals the spatially resolved displacement in the film. Thereby, information about the profile of the energy deposition in the film as well as about the mechanical interaction with the substrate material is obtained.

show abstract

Section: Resultssupporting

confidence: 64%

“…The observed values match the speed of sound of the corresponding transverse acoustic (TA) and longitudinal acoustic (LA) modes in single crystals. 25…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Tuning and Tracking of Coherent Shear Waves in Molecular Films

Lemke¹,

Breiby

Ejdrup³

et al. 2018

ACS Omega

View full text Add to dashboard Cite

show abstract

“…Measuring the phonon band structures of molecular crystals is, however, quite challenging, as it typically requires large single crystals of fully deuterated materials . In fact, to the best of our knowledge, to date, only the phonon band structures (simultaneously characterizing phonon frequencies and wave vectors) of deuterated naphthalene, anthracene, and perylene have been measured with inelastic neutron scattering. − For more complex and/or nondeuterated organic materials, phonon densities of states (i.e., phonon spectra in which the wave vector dependence is not resolved) have been determined. ,,− More recently, inelastic X-ray scattering has been applied to determine parts of the dispersion of rubrene crystals, albeit still combined with a tremendous experimental effort . As an alternative approach, simulating phonons of OSCs employing state-of-the-art dispersion-corrected density functional theory provides accurate Γ-point phonon frequencies. ,− Even more importantly, for the aforementioned deuterated naphthalene, they also accurately reproduce the measured phonon band structures. ,, Simulations have the additional advantage that they provide access to quantities beyond phonon frequencies and their dispersion relation.…”

Section: Introductionmentioning

confidence: 99%

“… 30 In fact, to the best of our knowledge, to date, only the phonon band structures (simultaneously characterizing phonon frequencies and wave vectors) of deuterated naphthalene, anthracene, and perylene have been measured with inelastic neutron scattering. 30 − 32 For more complex and/or nondeuterated organic materials, phonon densities of states (i.e., phonon spectra in which the wave vector dependence is not resolved) have been determined. 25 , 28 , 33 − 35 More recently, inelastic X-ray scattering has been applied to determine parts of the dispersion of rubrene crystals, albeit still combined with a tremendous experimental effort.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Phonon Bands in H-Bonded Molecular Crystals: The Instructive Case of α-Quinacridone

Legenstein,

Reicht,

Kamencek

et al. 2023

ACS Mater. Au

View full text Add to dashboard Cite

Phonons play a crucial role in the thermodynamic and transport properties of solid materials. Nevertheless, rather little is known about phonons in organic semiconductors. Thus, we employ highly reliable quantum mechanical calculations for studying the phonons in the α-polymorph of quinacridone. This material is particularly interesting, as it has highly anisotropic properties with distinctly different bonding types (H-bonding, π-stacking, and dispersion interactions) in different spatial directions. By calculating the overlaps of modes in molecular quinacridone and the α-polymorph, we associate Γ-point phonons with molecular vibrations to get a first impression of the impact of the crystalline environment. The situation becomes considerably more complex when analyzing phonons in the entire 1st Brillouin zone, where, due to the low symmetry of α-quinacridone, a multitude of avoided band crossings occur. At these, the character of the phonon modes typically switches, as can be inferred from mode participation ratios and mode longitudinalities. Notably, avoided crossings are observed not only as a function of the length but also as a function of the direction of the phonon wave vector. Analyzing these avoided crossings reveals how it is possible that the highest frequency acoustic band is always the one with the largest longitudinality, although longitudinal phonons in different crystalline directions are characterized by fundamentally different molecular displacements. The multiple avoided crossings also give rise to a particularly complex angular dependence of the group velocities, but combining the insights from the various studied quantities still allows drawing general conclusions, e.g., on the relative energetics of longitudinal vs transverse deformations (i.e., compressions and expansions vs slips of neighboring molecules). They also reveal how phonon transport in α-quinacridone is impacted by the reinforcing H-bonds and by π-stacking interactions (resulting from a complex superposition of van der Waals, charge penetration, and exchange repulsion).

show abstract