Ionic Two-Sublattice Liquid Model

Within the framework of the CEF, the ionic two-sublattice liquid (I2SL) model was developed to be used when there is a tendency for ionization in the liquid, which happens in liquid oxides and sulphides for example. The same model can be used both for metallic and oxide melts. At low levels of oxygen, the model becomes equivalent to a substitutional solution model between metallic atoms. Two sublattices are assumed, one containing charged cations and one containing charged anions, neutrals and vacancies. The complication for an ionic liquid is that the numbers of sites on the cation sublattice and anion sublattice vary with the composition to preserve electroneutrality. For a comprehensive description on the I2SL model, see [1985Hil; 1991Sun]. In these references, the possible excess parameters are also discussed. Type code Y is used for the I2SL model.

Examples of phase definitions in a setup-file:

ENTER_PHASE LIQUID Y,

     AL+3,CR+2,FE+2,NI+2; VA; N N

ENTER_PHASE IONIC_LIQ Y,

     CA+2,MG+2; O-2; N N

ENTER_PHASE IONIC_LIQ Y,

     AL+3,CA+2,FE+2,MG+2,SI+4;

     ALO2-1,O-2,SIO4-4,VA,FEO3/2,SIO2; N N

References

[1985Hil] M. Hillert, B. Jansson, B. Sundman, J. Ågren, A two-sublattice model for molten solutions with different tendency for ionization. Metall. Trans. A. 16, 261–266 (1985).

[1991Sun] B. Sundman, Modification of the two-sublattice model for liquids. Calphad. 15, 109–119 (1991).