Effects of Strong Electrostatic Correlation on the Solvation Energy of Ions: Comparison of the Modified Born Energy with Experiments

The Born solvation energy of the ions immersed in liquids is invoked in a vast literature, but it is often inadequate to explain experimental data without adjusting the model parameters, such as the ionic radius and the dielectric constant of solvents. To improve this situation, we have developed a coarse-grained theory of ion solvation in liquids, which draws upon a Ginzburg-Landau type of theory. Our theory accounts simultaneously for the dielectric inhomogeneity and strong electrostatic correlation near the ions. Our result modifies the conventional Born solvation energy using a model parameter that describes the electrostatic correlation length. We show that the outstanding consistency between the theory and experiment--without assuming hypothetical ionic radii in cases of various ions, pure liquids, and even liquid mixtures--is remarkable. Examples include eight different liquids with twelve monovalent, fifteen divalent, and ten trivalent ions. We also mention the application of our theory to the phase instability of a mixture of a polymer and an ionic liquid.