Local density augmentation in attractive supercritical solutions: Inhomogeneous fluid approach

We study the local solute-solvent structure in supercritical solutions, using as a model system a dilute Lennard-Jones solute in a supercritical Lennard-Jones fluid. The study is focused on attractive mixtures, which are characterized by enhanced local solvent density around the solute molecule. We employ the integral equation theory for inhomogeneous fluids to calculate the solute-solvent radial distribution function and the local coordination number of the solute. We show that this theory is in excellent agreement with Monte Carlo simulations and provides a substantial improvement over the integral equation theory formulated for homogeneous fluids. Using the inhomogeneous fluid theory, we perform a detailed study of the local density enhancement in attractive supercritical mixtures, and analyze its dependence on the model potential parameters and on the solvent thermodynamic conditions. (C) 2000 American Institute of Physics. [S0021-9606(00)51416-0].