Free Energy Perturbation Theories for Simple Fluids and Solids 163
difference between the mc and lc approximations for the excess energy, even at low
temperatures, and negligible for the EOS. For shorter-ranged HCY fluids the theory
deviates appreciably from the simulation data at low temperatures. Concerning the
liquid–vapor coexistence, the results are quite good for κ 2.0, whereas for larger
values of κ the theory provides too high values for the coexistence curve in the T
∗
−ρ
∗
plane in the neighborhood of the critical point, and the deviation from simulations
increases with κ.
Better results for short-ranged attractive HCY fluids are obtained from the Zhou
third-order perturbation theory (Zhou 2006b), but still the predicted liquid–vapor
coexistence ...