Thermodynamic Re-assessment of the Nb-Zr System Using the CE–CVM Model for Solid Solution Phases.

The Nb-Zr system was reassessed based on calculated theoretical data and available thermodynamic and phase equilibria data. The Gibbs energies of the bcc and hcp solid phases were described using cluster expansion and cluster variation methods (CE–CVM) to model short-range ordering (SRO) in the solid solution phases. Enthalpy of mixing data was calculated using density functional theory with special quasirandom structures and cluster expansion (CE) method. A sub-regular solution model was used for describing the Gibbs energy of the liquid phase. An optimal set of parameters has been obtained for describing the Gibbs energies of the liquid and solid phases in the Nb-Zr binary system. The modeled phase diagram and thermodynamic properties agree with the experimental data. The relevance of CE–CVM has been demonstrated in the present case by calculating the solid phase's short-range order (SRO) parameters as a function of composition and temperature. [ABSTRACT FROM AUTHOR]