Abstract
A purely statistical mechanical approach is proposed to account for the liquid–vapor critical point based on the mean density approximation (MDA) of the direct correlation function. The application to hard-core Yukawa (HCY) fluids facilitates the use of the series mean spherical approximation (SMSA). The location of the critical parameters for HCY fluid with variable intermolecular range is accurately calculated. Good agreement is observed with computer simulation results and with the inverse temperature expansion (ITE) predictions. The influence of the potential range on the critical parameters is demonstrated and the universality of the critical compressibility ratio is discussed. The behavior of the isochoric and isobaric heat capacities along the equilibrium line and the near vicinity of the critical point is discussed in details.
► A statistical mechanical approach is used to account for the criticality of the liquid–vapor coexistence in simple fluids. ► The range of intermolecular potential is important for locating the critical parameters. ► We discussed the universality behavior of heat capacity at Tc.