Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 29: New materials
HL 29.2: Talk
Tuesday, February 26, 2008, 12:15–12:30, ER 164
Orientational ordering and intermolecular interactions in the rotor-stator compounds C60·C8H8 and C70·C8H8 under pressure — •Komalavalli Thirunavukkuarasu1, Chirstine A. Kuntscher1, Gyula Bényei2, István Jalsovszky2, Gyöngyi Klupp3, Katalin Kamarás3, Éva Kováts3, and Sándor Pekker3 — 1Experimentalphysik II, Universität Augsburg, D-86159 Augsburg, Germany — 2Department of Organic Chemistry, Eötvös Loránd University, P.O.Box 32, Budapest, Hungary H 1518 — 3Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences,P.O.Box 49, Budapest, Hungary H 1525
The fullerene-cubane molecular crystals C60·C8H8 and C70·C8H8 are the first members of the rotor-stator crystal family [1]. Static C8H8 molecules occupy the octahedral voids of the fullerene fcc structure and act as bearings for the rotating fullerene molecules. On cooling, C60·C8H8 undergoes a phase transition at 140 K due to orientational ordering of the C60 molecules, while C70·C8H8 undergoes transitions at around 390 K and 150 K. A first pressure-dependent transmittance study revealed an orientational ordering transition in C60·C8H8 induced at 0.8 GPa [2]. We have extended our spectroscopic studies to a broad frequency range for both C60·C8H8 and C70·C8H8 to monitor the vibrational properties and the absorption edge as a function of pressure. The nature of the observed anomalies and the electronic properties under pressure will be discussed. Supported by the DFG. [1] S. Pekker et al., Nature Materials 4, 764 (2005). [2] C. A. Kuntscher et al., Phys. Stat. Sol. (b) 243, 2981 (2006).