Electrostatic fluctuations in cavities within polar liquids and thermodynamics of polar solvation

TL;DR

This study uses numerical simulations to explore electrostatic fluctuations in cavities within polar liquids, revealing a transition in solvation thermodynamics at larger cavity sizes and a faster decay of fluctuations than traditional models predict.

Contribution

It demonstrates a size-dependent regime change in polar solvation thermodynamics and challenges existing electrostatic theories with new decay behavior of fluctuations.

Findings

Fluctuation variances decay faster than 1/R_0 for large cavities.

Thermodynamics of solvation changes dramatically at cavity sizes 4-5 times the liquid particle.

Large cavities exhibit interface softening not accounted for by current models.

Abstract

We present the results of numerical simulations of fluctuations of the electrostatic potential and electric field inside cavities created in the fluid of dipolar hard spheres. We found that the thermodynamics of polar solvation dramatically changes its regime when the cavity size becomes about 4-5 times larger than the size of the liquid particle. The range of small cavities can be reasonably understood within the framework of current solvation models. On the contrary, the regime of large cavities is characterized by a significant softening of the cavity interface resulting in a decay of the fluctuation variances with the cavity size much faster than anticipated by both the continuum electrostatics and microscopic theories. For instance, the variance of potential decays with the cavity size $R_0$ approximately as $1/R_0^{4-6}$ instead of the $1/R_0$ scaling expected from standard electrostatics. Our results suggest that cores of non-polar molecular assemblies in polar liquids lose solvation strength much faster than is traditionally anticipated.