Modern techniques of liquid state physics have been successfully used to probe the microscopic structure and dynamics of a variety of multicomponent liquids in which relative ordering of the species is present near freezing. The alkali halides are prototypes for this specific type of short-range order in relation to the nature of bonding, but the systems in question also include other monovalent and polyvalent metal-ion halides, alkali-based intermetallic compounds and chalcogen-based alloys. A viewpoint is taken in this review which gives attention to the relations between liquid and solid phase properties across melting for compound systems at stoichiometric composition. In addition, large deviations for stoichiometry can be realised in the liquid phase, to display trends of evolution of structure, bonding and electronic states with composition.

https://iopscience.iop.org/article/10.1088/0034-4885/49/9/002/pdf

Structure and dynamics of molten salts

The present understanding of how dipolar forces affect the structure and phase behaviour of classical fluids is reviewed. We focus mainly on the apparent absence of a liquid-vapour phase transition for strongly polar spherical particles, and discuss how the same can be recovered. By concentrating on theoretical and simulation studies of simple models, the roles and interplay of dipolar and Van der Waals interactions and molecular shape can be clearly discerned. Connection is made with experimental work on ferrofluids. Finally, we discuss the theoretical and computational challenges that lie ahead.

http://iopscience.iop.org/article/10.1088/0953-8984/12/33/201/pdf

The effect of dipolar forces on the structure and thermodynamics of classical fluids

We extend the application of the mode‐coupling theory for the dynamics of critical fluctuations in fluids into the non‐asymptotic critical region. An approximate solution of the mode‐coupling equations yields a set of representative equations for the thermal conductivity and the viscosity of one‐component fluids which incorporates the crossover from asymptotic singular behavior near the critical point to the regular behavior of these transport properties far away from the critical point. The equations for the critical enhancements of the thermal conductivity and the viscosity depend on the background transport properties of the fluid, the equilibrium thermodynamic properties of the fluid, and one fluid‐dependent wave‐number cutoff qD, which is indicative of the crossover length scale. We compare our crossover model with experimental data for the thermal diffusivity, the thermal conductivity, and the viscosity of carbon dioxide and ethane.

Non‐asymptotic critical behavior of the transport properties of fluids

Dielectric Constants of Fluid Models: Statistical Mechanical Theory and its Quantitative Implementation

Structure and dynamics of simple ionic liquids

Correlation functions of various local thermodynamic variables of binary mixtures are obtained from the linearized hydrodynamic equations following the method of Mountain and Deutch. “Non-Lorentzian” parts of the time Fourier transformed correlation functions which have not been included by these authors are obtained here and their effect on the light scattering spectrum considered. An extension of the treatment by Fox and Uhlenbeck of Landau and Lifshitz hydrodynamical fluctuation theory to binary mixtures has been accomplished and correlation functions of the "fluctuating forces" are obtained for this case.

Hydrodynamic Correlation Functions for Binary Mixtures

The thermodynamics of two recent models of hard-sphere polar fluids is investigated. The two models are the Onsager model developed by Nienhuis and Deutch and the mean spherical approximation results obtained by Wertheim. The equation of state, vapour pressure curve, and other pertinent thermodynamic properties are determined. These results for the pure hard-sphere polar fluid complement the results recently reported by Rushbrooke, Stell and Hoye. The thermodynamics of simple multicomponent hard-sphere polar mixtures is examined for the case of equal hard-sphere radii. Results for the multicomponent MSM are based on the exact solution of this model by Adelman and Deutch. The Onsager model is generalized to the case of many components. For both multicomponent models it is demonstrated that a variety of regions of instability exist for the one-phase fluid. Finally a discussion is included of how well these models agree with experiment.

J.W.H. Sutherland

Papers

Hydrodynamic Correlation Functions for Binary Mixtures

Thermodynamics of pure and multicomponent dipolar hard-sphere fluids

Light scattering from a binary mixture with internal relaxation