Calculation of the Isochoric Heat Capacity of Argon from the Gas to the Solid Phase Using the Molecular Dynamics Method

Using the molecular dynamics method, the temperature dependence of the isochor- ic heat capacity of argon was calculated from the gas phase to the solid phase at a constant density of 109.4 kg/m³ and a cooling rate of 10⁹ K/s. The isochoric heat capacity of argon, Cᵥ, is determined from the slopes (dE/dT) of line segments obtained by discrete approxima- tion of the internal-energy temperature dependence, using a temperature increment of 5 K. The temperature-dependent plots of the isochoric heat capacity of the argon particle system show characteristic jumps corresponding to the gas–liquid and liquid–solid phase transi- tions. It was observed that, in the solid phase of argon, decreasing temperature leads to a re- duction in the derivative dCᵥ/dT, which is associated with the formation of particle clusters and macroscopic voids in the argon structure.