A Model to Predict Ionic Disorder and Phase Diagrams: Application to CaO-MgO, Gd2O3-ZrO2, and to Sodium β′′-alumina

A model for the computation of ionic disorder and phase diagrams in complex oxides is presented. The model is based on a successive integration of the degrees of freedom in the material and can be combined with first-principles techniques to make predictions without the need for experimental data. We show applications on CaO-MgO, Gd2O3-ZrO2, and sodium β′′-alumina. For CaO-MgO the solid solubility limits are predicted in good agreement with experiments. both Gd2O3-ZrO2 and sodium β′′-alumina show a coupled order-disorder transition where two sublattices undergo an ordering transition simultaneously.