Thermodynamic modeling in glass-forming melts

Thermodynamic database computing systems combine extensive databases with general software for calculating the conditions of chemical equilibrium. Databases for non-ideal solution phases are obtained by critical evaluation of available data on sub-systems to obtain optimized parameters of model equations. With the advent of models and evaluated databases for oxide melts/glasses, these computing systems have many applications of interest in glass science and engineering which are demonstrated by sample calculations in the present article. First, the authors' modified quasichemical model for the melt/glass phase is reviewed. Following this, a new critical evaluation/optimization of the Na2O-CaO-SiO2 system is presented. Finally, the authors' model for the chemical dissolution of gases as sulfate, sulfide, phosphate, halide and carbonate in oxide melts/glasses is reviewed. Solubilities are calculated a priori, from a knowledge of the thermodynamic activities of the component oxides, with no adjustable parameters. Agreement with measurements is obtained within experimental uncertainty for solubilities in multicomponent oxide melts/glasses over a wide range of components and compositions. (C) 1999 Elsevier Science B.V. All rights reserved.