Solute-solvent size ratio dependence of the solute residual chemical RESEARCH NOTE potential in subcritical solvents

Abstract

We investigated the dependence of the solute residual chemical potential on soluteto-solvent molecule size ratio in infinitely dilute Lennard-Jones fluids. A minimum on the μ_A ^r∞/ε_BB ∼ (σ_AB/σ_BB)³ curve has been found at high solvent densities ρσ_BB ³ = 0•75 and 0•8 (σ and ε are the Lennard-Jones size and energy parameters, respectively, μ_A ^r∞ is the solute residual chemical potential in an infinitely dilute solution, A and B denote solute and solvent, respectively, and ρ is the solvent molecule density). Such a minimum commonly has been observed in supercritical fluids, but obtaining one from computer simulation of subcritical fluids is challenging since a very high solvent density or a large solute size is needed. This study seems to provide the first simulation evidence of such a minimum at a subcritical temperature. The position of this minimum is very sensitive to solvent density as well as temperature. An umbrella sampling Monte Carlo method was adopted to compute the solute residual chemical potentials in infinitely dilute solvents. BB A