Phase diagram for the Lennard-Jones fluid modelled by the hard-core Yukawa fluid

The liquid-gas phase diagram for the Lennard-Jones (LJ) fluid model is obtained using the mean spherical approximation (MSA) for the corresponding hard-core Yukawa fluid. The calculated phase diagram is compared with the phase diagrams for the LJ fluid predicted by the Gibbs ensemble Monte Carlo simulation, and by the Percus-Yevick (PY) and reference hypernetted chain (RHNC) theories. The accuracy of the MSA is comparable with the accuracy of the PY approximation. Although the MSA is less accurate than the RHNC approximation, it has an important advantage of being solvable along the whole liquid-gas coexistence curve, including the vicinity of the critical point.