Ionic solvation in polar supercritical fluids: an integral equation study

A theoretical study of ion solvation in a polar supercritical solvent is reported. The solute–solvent microstructure is computed from the nonlocal integral equation theory and is shown to be in good agreement with simulation results. The nonlinear behavior of the solvation free energy of the ion in a highly compressible supercritical regime is rationalized in terms of a strong electrostriction effect. It is shown that the accuracy of the Born expression for the solvation energy can be substantially improved by taking into account the local solvent density augmentation around the ionic solute.