The modified quasichemical model in the Distinguishable-Pair Approximation for multicomponent solutions

Abstract

The Modified Quasichemcial Model in the Distinguishable-Pair Approximation (MQMDPA) for manifold short-range orders in liquids has been successfully extended to multicomponent solutions. The extension is conducted by means of the geometrical interpolation method. Three types of interpolation models, namely Kohler, Toop and Chou, are introduced to initially formulate the pair interaction energies in ternary solutions by employing those in their constituent binary solutions. The pair energies can be expanded in terms of the pair fractions (configuration-dependent) or in terms of the coordination-equivalent fractions (composition-dependent). These methods are subsequently extended for use in multicomponent solutions. A general formalism for the combined Kohler-Toop model is employed to permit complete freedom of choice to treat any ternary subsystems with a symmetric or asymmetric model. Meanwhile, a general Chou model is also used to treat all ternary subsystems without any human interference to select symmetric or asymmetric components but only dependent upon the similarity and difference in properties from each two binary solutions with a co-member. Advantages and shortcomings are critically discussed regarding the utilization of different interpolation models.