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a b s t r a c tThe FactSage computer package consists of a series of information, calculation and manipulation modules that enable one to access and manipulate compound and solution databases. With the various modules running under Microsoft Windows s one can perform a wide variety of thermochemical calculations and generate tables, graphs and figures of interest to chemical and physical metallurgists, chemical engineers, corrosion engineers, inorganic chemists, geochemists, ceramists, electrochemists, environmentalists, etc. This paper presents a summary of the developments in the FactSage thermochemical software and databases during the last six years. Particular emphasis is placed on the new databases and developments in calculating and manipulating phase diagrams.

Further improvements to the modified quasichemical model in the pair approximation for short-range ordering in liquid and solid solutions are presented. The energy of pair formation is expanded in terms of the pair fractions rather than the component fractions, and coordination numbers are permitted to vary with composition. A formalism is introduced whereby the quasichemical equations are shown to be equivalent to the equations of an associate model if the pairs are formally treated as fractional associates. The model is applied to the liquid phase in a new optimization of the KCl-MgCl 2 system.

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