Prediction of the thermodynamic functions of mixing of binary oxide melts in the PbO-SiO2, Al2O3-SiO2 and CaO-Al2O3 systems by structure-based modification of the quasi-chemical model

A structure-based modification of the Guggenheim's quasi-chemical model for the prediction of the thermodynamic functions of mixing in binary silicate and aluminate melts is presented and the extension of this approach to ternary systems is discussed. Based on the “anionic” point of view on the oxide melts structure, the novel method for determination of the interchange energy (a principal parameter of the quasi-chemical theory) was proposed along with a simple and general set of the equations. The activity calculations of the end-member components and integral and partial enthalpies and Gibbs free of mixing along with the whole range of compositions for PbO-SiO2 and Al2O3-SiO2 systems as well as the model calculations of components in CaO-Al2O3 melts were made. The reasonable agreement between results of model calculations and experimental data showed the reliability of this approach in predicting of the thermodynamic functions of mixing in binary and aluminate systems. This approach has the advantage that prior knowledge of the experimental mixing properties of liquid oxide systems is not required.