Molecular Simulation Study of the Vapor–Liquid Interfacial Behavior of a Dimer-forming Associating Fluid

Grand-canonical transition-matrix Monte Carlo simulation is applied to analyze the effect of molecular association on the vapor–liquid coexistence and interfacial behavior of square-well based dimerizing fluids. Finite-size scaling techniques are implemented in conjunction with histogram reweighting to determine the infinite-system surface tension from a series of finite-size simulations. The effect of strength of association and size of association site on coexistence densities, pressure, surface tension, and monomer fraction is presented. Some qualitative features of the dependence of monomer fraction and surface tension on association strength are found to disagree with behavior expected from previous studies using the statistical associating fluid theory (SAFT). Comparison with experimental data shows that molecular models must incorporate an explicit association interaction in order to describe the surface-tension behavior of a real dimerizing fluid (acetic acid).