Heat capacity and raman scattering in C70 crystal

Successive structural phase transitions in C70 crystal were studied by heat capacity and Raman scattering. Heat capacity was measured between 4.2 and 350 K by means of the ac calorimetry. We observed two anomalies at 62 K and around 255 K. The latter is assigned as an orientational ordering transition in the molecular rotation about the long axis. The 62-K anomaly probably comes from the freezing of the jumping motion. Raman spectra of C70 crystal were measured in the temperature region 14-340 K. A weak Raman peak at 1089 cm−1 appear below about 152 K, but no anomaly was found at this temperature in the heat capacity.