Equivalence of the generalized bond-energy model, the Wagner-Schottky-type model and the compound-energy model for ordered phases

The equivalence of three thermodynamic models used in the literature to describe the compositional and temperature dependencies of the thermodynamic properties of ordered intermetallic phases is presented. The three models are the generalized bond-energy model, the Wagner-Schottky-type model and the compound-energy model. Equations to convert the model parameters of the generalized bond-energy model to those of the other two models are derived. The validity of these equations is demonstrated by showing the successful conversion of the model parameters for the ordered phases in the Ti-Al system from the generalized bond-energy model to those of the Wagner-Schottky-type model and the compound-energy model. However, conversion of the model parameters from these two models to the generalized bond energy model is generally not possible due to additional constraints imposed in developing the later model.