Square-well chain mixture: analytic equation of state and Monte Carlo simulation data

An analytic perturbation theory equation of state developed for mixtures of freely-jointed square-well chain fluids of variable well width is tested a gainst Monte Carlo simulation data. The equation of state is based on secon d-order Barker and Henderson perturbation theory to calculate the thermodyn amic properties of the reference sphere fluid, and on first-order Wertheim thermodynamic perturbation theory to account for the connectivity of sphere s to form chains. A real function expression for the radial distribution fu nction of hard spheres and one-fluid type mixing rule are used to obtain an analytic, closed form expression, for the Helmholtz free energy of mixture s of square-well spheres. In order to test the theories, Monte Carlo simula tions for binary mixtures of square-well chains were performed to obtain th e radial distribution function at the contact point, the compressibility fa ctor, and the configurational internal energy of these mixtures, The propos ed equation of state leads to good predictions of compressibility factor of square-well chains and their mixtures when compared with the simulation da ta. (C) 2001 Elsevier Science B.V. All rights reserved.