Recent developments in the significant structure theory of liquids

Abstract

As the important structures in explaining the properties of liquids, the significant structure theory picks out three structures, the solid-like structure, the configurational degeneracy associated with a solid-like molecule, and the gas-like structure. In conjunction with these cardinal concepts, it also follows from the model that the portion of the solid-like part is V s V and another portion ( 1− V s V ) is the gas-like part where V and V s are the molar volumes of the liquid and of the solid, respectively. Using this model, the partition function of liquid is formulated, and the thermodynamic properties are calculated with good agreement with experiment. The significant structure theory is applicable for calculating transport properties, such as viscosity, the diffusion coefficient and the thermal conductivity, with good results. It is also applicable for deriving the adsorption isotherms of rare gases on graphite by assuming that the adsorbate forms a two dimensional liquid. Further tests of the significant structure theory are made by applying it to the systems of hard spheres and hard disc, and by comparing the calculated thermodynamic properties with the results of computer calculations by the Monte Carlo or molecular dynamics method. The agreement is excellent. The significant structure theory is also applicable to liquid mixtures, for example, the binary mixtures of Ar and N 2, Ar and O 2, and O 2 and N 2. The calculated excess-properties such as the heat content. Gibbs free energy and molar volume agree satisfactorily with experiment.