Thermodynamic properties of fullerite C70

Abstract

A new expression for the isochoric heat capacity and the equation of state of fullerite C₇₀ are obtained in the framework of a quantum-statistical method. Analogs of the Debye law and Dulong–Petit law for this fullerite are formulated. Fullerene C₇₀ molecules are modeled by isotropic quantum oscillators under the assumption that their nonsphericity weakly influences the thermodynamic properties of the condensed phase. The intramolecular oscillations of carbon atoms are described using the Debye theory and the cold contribution to the free energy of fullerite is calculated using the Lennard-Jones pair potential for fullerene molecules. A comparison of the proposed theory to experiment shows good agreement.