Analytical molecular-based equation of state applied to dense supercritical Buckingham Exp(α,m) fluids modelled by two-Yukawa potentials and application to the N2 fluid

In this Short Communication an efficient procedure to fit closely the repulsive part of a given spherical intermolecular potential phi(r) with a two-Yukawa function is introduced and applied to the general Buckingham Exp (alpha, m) fluid. The method consists first in imposing the same minima and then equating the values of both potentials deep into the positive repulsive branch at a suitable distance. The recently developed Ross analytic (RA) variation perturbation theory for two-Yukawa (TY) fluids with correction terms (RAC theory) to account for the remaining discrepancies between both potentials is then applied to the analytic determination of the nitrogen N2 pressure at high temperatures and high densities from its known Buckingham intermolecular potential Exp(alpha = 12.684, m = 6). The results compare favourably with experimental results and recent extensive molecular dynamic (MD) simulation data.