Screened Coulombic Orientational Correlations in Dilute Aqueous Electrolytes

TL;DR

This paper explains long-range orientational order in dilute aqueous electrolytes using the Ornstein-Zernike approach, highlighting the roles of electroneutrality, dipolar interactions, and screening, supported by molecular dynamics simulations and experiments.

Contribution

It provides a quantitative theoretical framework for ion-induced orientational correlations in water, extending understanding beyond hydrogen-bonding solvents.

Findings

Long-range orientational order is explained by the Ornstein-Zernike theory.

Numerical theories recover classical analytical expressions.

The effect is governed by electroneutrality, dipolar interactions, and screening.

Abstract

The ion-induced long-range orientational order between water molecules recently observed in second harmonic scattering experiments and illustrated with large scale molecular dynamics simulations is quantitatively explained using the Ornstein-Zernike integral equation approach of liquid physics. This general effect, not specific to hydrogen-bonding solvents, is controlled by electroneutrality condition, dipolar interactions and dielectric+ionic screening. As expected, all numerical theories recover the well-known analytical expressions established 40 years ago.