Thermodynamic modeling of the La-B and La-Bi systems supported by first-principles calculations

Thermodynamic assessments of the La-B and La-Bi systems were carried out based on the available experimental data including thermodynamic properties and phase equilibria by means of the CALPHAD method. The enthalpies of formation at 0 K for the LaB₄, LaB₆, La₂Bi, La ₅Bi₃, La₄Bi₃ and LaBi were computed via first-principles calculations. These enthalpies of formation were used "key experimental data" in the CALPHAD approach in order to obtain the thermodynamic parameters with sound physical meaning. The liquid phase has been modeled with both the substitutional solution model and associate model, and two sets of self-consistent thermodynamic parameters for the La-B and La-Bi systems were finally obtained. The calculated phase diagram and thermodynamic properties agree reasonably with the literature experimental data and the present first-principles calculations.