Reference hypernetted chain theory for linear molecular fluids: A comprehensive study of the gas-liquid coexistence

We have used the reference hypernetted chain theory (RHNC) with a hard-core reference fluid treated in the modified Verlet's approximation (VM) to obtain the gas-liquid coexistence curve of centrosymmetric linear molecular fluids modeled via site-site Lennard-Jones interactions with and without electrostatic forces. Explicit results are presented for the gas-liquid equilibrium of molecular nitrogen and carbon dioxide. Thermodynamic consistency constraints are crucial to define the reference system. Comparison with Gibbs Ensemble Monte Carlo and density functional theory (DFT) calculations evidence the RHNC-VM theory is an excellent tool for predicting coexistence densities and vapor pressures of linear molecular fluids. (C) 1996 American Institute of Physics.