# Ionic activity in concentrated electrolytes: solvent structure effect revisited

## TL;DR

This paper investigates how solvent structure influences electrolyte activity coefficients in concentrated solutions using a non-local dielectric model, revealing over-screening effects and providing analytical expressions that align with experimental data.

## Contribution

It introduces a non-local dielectric function approach with an interpolated formula, offering a new perspective on solvent effects in electrolyte activity modeling.

## Key findings

- Over-screening and oscillations in potential around ions
- Closed-form expressions for activity coefficients
- Good agreement with experimental data

## Abstract

We revisit the role of the local solvent structure on the activity coefficient of electrolytes with a general non-local dielectric function approach. We treat the concentrated electrolyte as a dielectric medium and suggest an interpolated formula for the dielectric response. The pure water limit is calibrated based on MD simulations and experimental data. Solving our model around a central ion, we find strong over-screening and oscillations in the potential, which are absent in the standard "primitive model" predictions. We obtain mathematically tractable closed-form expressions for the activity coefficients and show reasonable agreement with experimental data.