Analytical equation of state based on the Ornstein-Zernike equation

A new two-Yukawa function is found to mimic very closely the Lennard-Jones potential. Simple analytical expressions are developed for the structure and thermodynamic properties of the Lennard-Jones fluid, utilizing the new function. The results from the expressions developed are satisfactorily compared with the Monte Carlo simulation data, the theory of Weeks et al. and the latest 33-parameter equation of state (EOS). The phase diagram of the Lennard-Jones fluid is also well predicted by the new EOS. The properties of four real fluids (argon, methane, oxygen and nitrogen) are calculated using the present EOS. Some noticeable improvements over the Peng-Robinson EOS are found for the calculation of saturated liquid densities and second virial coefficients.