A Short History of Phase Transitions in Ionic Fluids

Abstract

The paper reviews the development of theory and experiments concerning the nature of the critical point in ionic fluids. Because of the long-range nature of the Coulomb interactions the possibility of mean-field critical behaviour was discussed as a possibility. Although some experiments supported mean-field criticality, simulations on the model fluid of charged hard spheres and later experiments on ionic solutions have shown that phase transition of ionic systems belong to the Ising universality class like phase transitions in non-ionic fluids. Experiments concerning the crossover from Ising to mean field-behaviour are discussed as well as systematic differences between the phase behaviour predicted for the model fluid of charged hard spheres and that observed in ionic solutions.

Thermodynamics of Liquid–Liquid Criticality in Supercooled Water in a Mean-Field Approximation

“…According to this scenario, there may exist deep in the supercooled region of metastable water a line of first-order transitions between two liquid phases, namely, a low-density liquid and a high-density liquid, terminating in a critical point. This critical point, like all other critical points in fluids, is assumed to belong to the three-dimensional Ising-model universality class [11][12][13]. Hence, in this scenario, the observed anomalies in the heat capacity [14], compressibility [15], and thermal expansivity [16] result from the divergence of density and entropy fluctuations at a liquid-liquid critical point (LLCP).…”

Mesoscopic structural and dynamic organization in ionic liquids

“…[40,41] It should be noted that the domain structure in solutions must be distinguished from the fluctuations of the composition [42,43] that are the precursors of phase separation observed in many solutions of ILs [44,45].…”

Critical Locus of Aqueous Solutions of Sodium Chloride Revisited

“…Second, there is considerable evidence that molecular, as well as ionic fluids, belong to the critical universality class of Ising-like systems [12,13]. For Ising-like systems, the critical behavior is characterized by two independent scaling fields, h 1 and h 2 , and one dependent scaling field, h 3 , which are analytic functions of the physical fields.…”