# Mean-Field Theory of Water-Water Correlations in Electrolyte Solutions

## TL;DR

This paper develops a mean-field theoretical model to explain long-range water-water correlations induced by ions in electrolyte solutions, aligning with experimental and simulation data.

## Contribution

It introduces an analytical expression extending Debye-Hückel theory to quantify ion-induced dipole-dipole correlations in water molecules.

## Key findings

- Model agrees with molecular dynamics simulations.
- Provides a qualitative understanding of ion-induced water correlations.
- Serves as a foundation for further theoretical research.

## Abstract

Long-range ion induced water-water correlations were recently observed in femtosecond elastic second harmonic scattering experiments of electrolyte solutions. To further the qualitative understanding of these correlations, we derive an analytical expression that quantifies ion induced dipole-dipole correlations in a non-interacting gas of dipoles. This model is a logical extension of Debye-H\"uckel theory that can be used to qualitatively understand how the combined electric field of the ions induces correlations in the orientational distributions of the water molecules in an aqueous solution. The model agrees with results from molecular dynamics simulations and provides an important starting point for further theoretical work.