Methods for calculating equilibrium properties of pure substances, considering the critical point features

Abstract

This paper deals with a fundamental equation of state for matter (FEoS). When constructing FEoS, the method of pseudocritical points (PCP) is used. The PCP method is based on the Benedek hypothesis and a new representation of the scale hypothesis of the critical point. We show the possibility to construct FEoS of argon based on the PCP method with the following characteristics: (i) FEoS is transformed into the virial equation of state in the region of small densities; (ii) FEoS is transformed into the Widom equation in the region of the critical point; (iii) FEoS has its working area with pressure (0 ≤ p/pc ≤ 740), density (0 ≤ p/pc ≤ 3.2) and temperature (83.8058 ≤ T ≤ 2300∼K) in. We compare FEOS with a number of known equations of argon state and discuss the results.