Electrostatic Potential of Phase Boundary in Coulomb Systems

TL;DR

This paper investigates the electrostatic potential difference at phase boundaries in Coulomb systems, showing it depends solely on temperature, vanishes at critical points, and can be numerically calculated for various models.

Contribution

It introduces a thermodynamic description of interface potential drops in Coulomb systems and provides numerical calculations for simplified models and real phase transitions.

Findings

Potential drop depends only on temperature

Drop tends to zero at critical point

Numerical simulation confirms theoretical predictions

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. This 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 coexistence curve) is an individual substance coefficient. The drop tends to zero at the critical point of the gas-liquid phase transition. A special critical exponent can be defined to describe this behavior. The value of the discussed potential drop is directly calculated by numerical simulation of phase transitions in Coulomb systems. Properties of the interface potential drop are discussed for several simplified Coulomb models (melting and evaporation in the One Component Plasma (OCP)). Some examples of phase transition in real situations are also discussed.