A new simple analytic equation of state for square-well chain fluids with variable width, 1.1 < λ < 2, based on perturbation theory and an analytic representation of the hard-sphere radial distribution function g HS(r)

Abstract

A new, simple and analytic perturbation theory equation of state for square-well chain fluids of variable well width (1.1 < λ < 2) is proposed. It is based on the recently developed, infinite-order Barker and Henderson perturbation theory for the thermodynamic properties of the reference monomer square-well fluid [J. Chem. Phys. 124 (2006) 154505], the statistical associating fluid theory to account for chain formation, and the new analytical expression of the radial distribution function of hard spheres developed by Sun in terms of a polynomial expansion of nonlinear base functions [Can. J. Phys. 83 (2005) 55]. The various integrals appearing in the theory are then simply evaluated in closed form. The compressibility factor and the internal energy thus obtained are in overall good agreement with existing computer simulation data for dimer, 4-mer, 8-mer and 16-mer square-well chain fluids at different well-width. Moreover the compressibility factors also compare favorably with those obtained from six other square-well chain fluids equations of state.