Explicit Solvents Reverse Temperature Dependence of Phase Behavior in Charged Fluids
Abstract
In most theories of electrolyte and polyelectrolyte solutions, the solvent is treated implicitly as a dielectric continuum. While this approximation has enabled major advances, it neglects coupling between ionic and dipolar degrees of freedom. Using molecular dynamics simulations and the mean-spherical approximation, we show that this coupling qualitatively alters electrostatically driven phase behaviour. At finite ion concentrations, many-body ion-dipole correlations reverse the temperature dependence of effective electrostatic interactions, leading to upper-critical solution temperature (UCST) behaviour in direct contrast to the lower-critical solution temperature (LCST) behaviour predicted by implicit-solvent electrostatic theories. This phase reversal arises from ion-induced suppression of local dipolar screening, a collective effect inaccessible to pairwise implicit-solvent descriptions.
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BibTeX
@misc{walker2026explicit,
title = {{Explicit Solvents Reverse Temperature Dependence of Phase Behavior in Charged Fluids}},
author = {Pierre J. Walker and Zhen-Gang Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.14366},
eprint = {2610.14366},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.14366},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Explicit Solvents Reverse Temperature Dependence of Phase Behavior in Charged Fluids
AU - Pierre J. Walker
AU - Zhen-Gang Wang
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2610.14366
UR - https://arxiv.org/abs/2610.14366
AB - In most theories of electrolyte and polyelectrolyte solutions, the solvent is treated implicitly as a dielectric continuum. While this approximation has enabled major advances, it neglects coupling between ionic and dipolar degrees of freedom. Using molecular dynamics simulations and the mean-spherical approximation, we show that this coupling qualitatively alters electrostatically driven phase behaviour. At finite ion concentrations, many-body ion-dipole correlations reverse the temperature dependence of effective electrostatic interactions, leading to upper-critical solution temperature (UCST) behaviour in direct contrast to the lower-critical solution temperature (LCST) behaviour predicted by implicit-solvent electrostatic theories. This phase reversal arises from ion-induced suppression of local dipolar screening, a collective effect inaccessible to pairwise implicit-solvent descriptions.
ER -