Contrasting Dielectric Properties of Electrolyte Solutions with Polar and Polarizable Solvents

We examine the dielectric constant of electrolyte solutions with a polar and/or polarizable small-molecule solvent using a classical field-theoretic approach. We compute corrections to the dielectric constant and screening length due to intra- and inter-molecular correlations via a self-consistent one-loop approximation, accounting for the excluded volume of both solvent and electrolyte. The theory predicts either a non-linear dielectric decrement or increment with increasing salt, depending on whether the fluid correlations are dominated by the dipolar or polarizable nature of the solvent. These contrasting regimes of non-linear dielectric behavior are consistent with those seen experimentally in high- and low-dielectric-constant electrolyte solutions.