Electrostatics of Phase Boundaries in Coulomb systems

TL;DR

This paper explores the electrostatic potential differences at phase boundaries in Coulomb systems, analyzing their thermodynamic properties, temperature dependence, and implications for simplified models and real systems using numerical and analytical methods.

Contribution

It provides a detailed analysis of the interface potential drop in Coulomb systems, highlighting its temperature dependence and critical behavior, with applications to simplified models and real materials.

Findings

Potential drop depends only on temperature, not surface properties.

At zero temperature, the potential drop relates to substance coefficients.

The potential drop vanishes at the critical point of phase transition.

Abstract

Any interface boundary in an equilibrium system of Coulomb particles is accompanied by the existence of a finite difference in the average electrostatic potential through this boundary. The discussed interface potential drop is a thermodynamic quantity. It depends on temperature only and does not depend on surface properties. The zero-temperature limit of this drop (along the coexistence curve) is an individual substance coefficient. At high temperature the drop tends to zero at critical point of gasliquid phase transition. A special critical exponent can be defined to describe this behavior. Study of the interface potential drop is illuminative in simplified Coulomb models: i.e. for melting and evaporation in variants of One Component Plasma model (OCP), or for model of Charged Hard/Soft Spheres (CHS/CSS) etc. In all these cases properties of the potential drop can be easily calculated by the DNS methods (direct numerical simulation) when the two-phase coexistence in Coulomb system is really simulated. Electrostatics of phase boundaries in real systems could be elucidated in analytical calculation of two-phase coexistence via finite-temperature DFT approach (density functional theory).