On the models of molecular associates in theories of thermodynamic properties for glass-forming melts

The basic statements of thermodynamic theories of nonideal solutions modeled as mixtures of molecular associates (groupings of constant composition) are reviewed. These models, when applied without additional assumptions, can explain only the negative deviations from an ideal behavior. As in the theory of regular solutions or in the Yokokawa-Niwa model of disintegrating glass-former network, the positive deviations should be introduced prior to the formulation of quasi-chemical equilibria. In view of the unavoidable difference in volumes between the groupings, it is expedient to describe their mixtures in terms of the Flory-Huggins theory. Consideration is given to the inconsistency of anionic polymeric models of oxide glasses, which is due to the use of the Temkin approximation.