An analytic equation-of-state for mixture of square-well chain fluids of variable well width

An analytic perturbation theory equation of state for a mixture of freely-j ointed square-well fluids of variable well width (1 less than or equal to h less than or equal to 2) is developed. The equation of state is based on s econd-order Barker and Henderson perturbation theory to calculate the therm odynamic properties of the reference sphere fluid, and on first-order Werth eim thermodynamic perturbation theory to account for the connectivity of sp heres to form chains. A real function expression for the radial distributio n function of hard spheres and a one-fluid type mixing rule are used to obt ain an analytic, closed-form expression, for the Helmohltz free energy of m ixtures of square-well spheres. Good results were obtained when this equati on of state was used with temperature-independent parameters to correlate v apor-liquid equilibrium data of pure substances and mixtures. (C) 2001 Else vier Science B.V, All rights reserved.