Phase transition in a simple plasma model

TL;DR

This paper investigates a gas-liquid type phase transition in a simple plasma model with charges of one sign, revealing its dependence on background assumptions and implications for phenomena like Wigner crystallization.

Contribution

It introduces a variational Double-OCP model and demonstrates the existence of a phase transition independent of background equation of state assumptions.

Findings

Phase transition depends on background compressibility assumptions.

Transition suggests possible anomalies in non-ideal plasma behavior.

Transition challenges the occurrence of Wigner crystallization in the model.

Abstract

A phase transition of gas-liquid type with an upper critical point is examined which arises in a model of charges of one sign on compensating background (OCP). The phase transition parameters are dependent on the detailed assumptions about the compressibility of the background, but the occurrence of this transition is independent on the background equation of state. In the electron-gas model ('jellium'), this transition appears to rule out Wigner crystallization. A variational principle in statistical mechanics is used to derive so-called Double-OCP model for a superposition of two one-component plasma models for charges of opposite sign. The free energy of this model sets an upper bound to that of a real plasma. Situations are discussed where this transition should manifest itself in anomalies in the approximate description of a non-ideal plasma.