A TWO-SUBLATTICE MODEL FOR MOLTEN SOLUTIONS WITH DIFFERENT TENDENCY FOR IONIZATION Mats Hillert,Bo Jansson,Bo Sundman and John Agren Div.of Physical Metallurgy.Royal Inst.of Techno- logy,S-100 44 Stockholm,Sweden Abstract Different models accounting for the introduction of an excess of cations or anions in an ionic melt are considered.A new model whchi describes the variation in the thermodynamic properties in a melt as it grabually changes its composition from purely metallic state to complete ionization is developed.The model is based upon Temkin's expression for the configurational entropy of mixing.Neutral species and hypothetic cal vacancies with an induced charge are introduced on the anion subla- ttice.The induced charge is equal to the average valency of the species occupying the cation sublattice.When the tendency of ionization is weak the model approaches the substitutional model.For binary systems the new model is formally identical to the associate solution model if the associates are defind in such a way that they contain one atom of the electronegative element.For higher-order systems the new model works with a lower number of composition variables and parameters than the associate solution model, 79一 日 七 ， ， ， ， 一 ， 七 刃 一 七 七 七 七 七 ， 吕 七 七 七 七 七 七 七 七 七 七 七 七 一 ￡ 七 七 ‘ 七 ， 导