Analytic equation of state and thermodynamic properties of diamond based on an analytic mean field approach

The analytic mean field potential (AMFP) method is applied to diamond. The analytic expressions for the Helmholtz free energy, internal energy and equation of state (EOS) are derived. The formalism for the case of the Morse potential is used in this work. The six potential parameters are determined by fitting the compression experimental data of diamond at ambient temperature. 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 for diamond. These results presented in this paper verify that the AMFP method is a useful approach to consider the anharmonic effects at high temperature. Numerous reasonable predictions and the change trend of the properties for diamond at extreme conditions have been given.