A comparison of some thermodynamic parameters between superhard fullerite, some metals and some covalent elements Original Research Article

Specific heat and sound velocities measurements were carried out on samples of C60 fullerene treated at high (up to 13 GPa) pressure and temperature (up to 1200 K). With an increase in specific gravity from 2.35 to 3.15 g/cm3 the specific heat decreases, but remains 7–8% higher than the specific heat of diamond. For the new materials obtained, the Debye temperature, the ΔC=Cp−Cv parameter, and the work of heat expansion were calculated in an ideal approach. Similar calculations were performed for graphite, diamond, silicon, germanium and some refractory metals for comparison. The results obtained made it possible to draw qualitative conclusions about the structural stability of the new materials and to trace general tendencies for different carbon substances. A C60 sample with specific gravity 3.15 g/cm3 had a hardness comparable with the hardness of diamond.