Comments On the heat capacity of liquids at high temperatures, S.M. Stishov, Physica A 478 (2017) 205

Abstract

It is shown that the isochoric heat capacity of dense gas, fluid and liquid decreases with increasing temperature at arbitrary values of a density for many pair interaction potentials, including bonded potentials; that a decrease of the isochoric heat capacity of the liquid with increasing temperature is related to a decrease of the interaction between the particles with increasing temperature; that a radial distribution function for nonideal dilute gas, which is independent of density, can describe a temperature dependence of the isochoric heat capacity of liquid argon; that a radial distribution function dependent on the density and temperature describes a temperature dependence of the isochoric heat capacity of liquid and dense fluid; that the Carnahan-Starling equation of state for soft spheres gives a good quantitative description of the isochoric heat capacity of argon; that the fluctuations of the kinetic energy increases with temperature faster than that of the potential energy; and finally, that a liquid state can be considered as a state of dense gas. The explicit expressions to define the Frenkel line on the (temperature, density) plane are derived.