Calculations of the thermal expansion, cohesive energy and thermodynamic stability of a Van der Waals crystal - fullerene C60

The temperature dependence of the intermolecular distance and the cohesive energy in the high-temperature modification of C60 solid fullerene was studied on basis of the correlative method of unsymmetrized self-consistent field. The central intermolecular potential of Girifalco and its approximation by Yakub were used. We conclude about the decisive role of anharmonic effects at high temperatures. The discrepancy between the calculated and experimental values of intermolecular distance does not exceed 0.8% on the whole temperature interval. The temperature of loss of thermodynamic stability was obtained (≈ 1915 K) and a possible melting temperature was estimated (≈ 1400 K). © 1994