Thermodynamic modeling of the Sr–X (X=H, Li, Na, Sc) systems

The Sr–X (X=H, Li, Na, Sc) systems are critically reviewed and modeled by means of the CALPHAD technique. The two-sublattice model is used to describe the solid solution phase in the Sr–H system, and the gas phase is treated as an ideal gas mixture of the species H, H2, Sr and Sr2. All the intermetallic compounds (αSrH2, βSrH2, Sr6Li23 and Sr3Li2) are treated as stoichiometric compounds. By means of first-principles calculations, the enthalpies of formation at 0 K for the Sr6Li23 and Sr3Li2 are computed with the desire to assist the thermodynamic modeling. No compound is found in the Sr–Na and Sr–Sc systems. A set of self-consistent thermodynamic parameters is finally obtained for each of these binary systems. Comparisons between the calculated and measured phase diagrams as well as thermodynamic properties show that most of the experimental information can be satisfactorily reproduced by the present thermodynamic descriptions.