Eur. Phys. J. B 16, 73-80 (2000)
https://doi.org/10.1007/s100510070251

Vibrational states of glassy and crystalline orthoterphenyl

¹ Fachbereich Physik, Universität Dortmund, 44221 Dortmund, Germany
² Max-Planck-Institut für medizinische Forschung, 69120 Heidelberg, Germany
³ Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany
⁴ Physik-Department E13, Technische Universität München, 85747 Garching, Germany
⁵ Institut Laue-Langevin, 38042 Grenoble, France

Corresponding author: ^a albert.toelle@unibas.ch

Received: 7 December 1999
Published online: 15 July 2000

Abstract

Low-frequency vibrations of glassy and crystalline orthoterphenyl are studied by means of neutron scattering. Phonon dispersions are measured along the main axes of a single crystal, and the corresponding longitudinal and transversal sound velocities are obtained. For glassy and polycrystalline samples, a density of vibrational states is determined and cross-checked against other dynamic observables. In the crystal, low-lying zone-boundary modes lead to an excess over the Debye density of states. In the glass, the boson peak is located at even lower frequencies. With increasing temperature, both glass and crystal show anharmonicity.