Structural Phase Transitions of Endohedral Metallofullerene La@C82 Studied by Single Crystal X-Ray Diffraction
- 1 March 2000
- journal article
- research article
- Published by Taylor & Francis in Molecular Crystals and Liquid Crystals
- Vol. 340 (1) , 639-642
- https://doi.org/10.1080/10587250008025539
Abstract
Recently we have succeeded to synthesize solvent-free single crystals of endohedral metallofullerene La@C82 with the size of 0.5×0.2×0.2mm3 for the first time. The low temperature (T) x-ray diffraction measurements (20K–300K) have elucidated successive phase transitions and the existence of four phases, (I) the face-centered cubic (fee) structure (300K–180K), (II) the rhombohedral structure (180K-140K), (III) the triclinic structure (140K–20K) and (IV) the simple cubic (sc) structure (132K-20K). The rhombohedral and triclinic phases are characterized by the C82-cage orientational order, while the sc phase is characterized by the molecular electric dipole order. In the fee phase, both are not in order. As for the two low-est-T phases, the crystal remains in the triclinic phase for slow cooling below 132K. On the other hand with rapid cooling, the crystal undergoes the phase transition to the sc phase at 115K, which is stable up to 132K. The sc phase is more stable than the triclinic phase, contrary to the usual cases.Keywords
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