Heat capacity measurements and thermodynamic studies of the new compound C60

Article abstract of DOI:10.1016/0921-4534(91)92016-5

Heat capacity of the new compound C₆₀ was measured by using a laboratory-made adiabatic calorimeter between liquid helium temperature and room temperature. A phase transition phenomenon was observed as a large heat capacity anomaly extending from 180 to 260 K. The fact that the anomaly has two peaks at 250 and 255 K indicates a complicated mechanism of the phase transition and/or some effects of purity, multi-phases in the sample. The values of enthalpy and entropy of transition were estimated as 6.7 kJmol^-1 and 28 JK^-1 mol^-1, respectively. The normal portion of the heat capacity curve as a whole is very similar to that of graphite. In the lowest temperature region, however, the heat capacity of C₆₀ is much larger than that of graphite. Molecular motion in the crystal of C₆₀ is discussed concerning with the lattice vibrations.