Correspondence of phase separation in several charged particle systems

Abstract

This paper demonstrates the close correspondence in phase‐separation behavior of a variety of systems which contain charged particles. These include electron‐hole fluids in semiconductors, oxide melts and glasses, and molten salts. Reduced critical parameters for the fifteen systems considered are calculated using the theory of corresponding states for ionic fluids. The reduced critical parameters are found to be in close agreement, indicating that the different systems exist in corresponding states at their critical points to a good approximation. A model of phase separation based on Debye–Hückel theory is presented. The usual limitations of the theory due to the linearization of the Poisson–Boltzmann equation as well as neglect of excluded volume effects due to hard core interactions are avoided by employing the dissociation/association equilibrium of Fuoss. The theoretical critical parameters which are derived are in excellent agreement with experimental data. The degree of dissociation is calculated to be about 3% at the critical point, which is in the expected range of a few percent.