Thermodynamic properties of solid FCC C84 based on an analytic mean field approach

Abstract

The analytic mean field potential (AMFP) approach is applied to the poly-exponential model solid. The analytic expressions for the Helmholtz free energy, internal energy and equation of state (EOS) are derived. The formalism for the case of the double-exponential (DE) model is applied to fcc C 84 . One set of potential parameters are determined by fitting the experimental compression data of C 84 up to 9.24 GPa at ambient temperature (297 K). The equilibrium distance and well depth for C 60 , C 70 and C 84 molecules are plotted. The thermophysical properties including the isothermals, thermal expansion, isochoric heat capacity, Helmholtz free energy and internal energy are calculated and analyzed. The theoretical results agree well with the experimental data available of C 84 . Basing the results of our calculations, we may also predict the behaviors of C 84 at extreme conditions.

Thermal properties of fullerites under high pressure and high temperature

“…Sun et al [10] showed that the AMFP is an analytic approximation of the free-volume theory. Yang et al [11] derived the analytical expressions for the EOS and the internal energy for the poly-exponential solid using AMFP method. The formulation is applied to the FCC C 70 solid.…”

“…Zubov et al [19] also used the Grifalco potential to study C 84 . Yang et al [11] studied the thermodynamic properties of solid FCC C 84 based on AMFP.…”