Thermodynamic assessment of the Ho–Te system supported by ab initio calculations

The phase diagram of the Ho–Te binary system has been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data of the phase equilibria and enthalpies of formation from ab initio electronic-structure calculations within the framework of density-functional theory. Reasonable models were constructed for all the phases of the system. The liquid phase was described as the substitutional solution model with excess energy expressed by Redlich–Kister polynomial. The compounds Ho2Te5 and HoTe3 were expressed as stoichiometric phases. The (HoTe) phase was modeled by two-sublattices; (Ho,Va)1(Te)1. A consistent set of thermodynamic parameters has been derived, and calculated phase diagram was compared with the experimental data. A good agreement between the calculated results and experimental data was obtained.

► We calculated enthalpies of formation of the HoTe and Ho2Te5 compounds by using ab initio method.
► We modeled the Gibbs energy of the HoTe intermediate phase for the first time.
► The thermodynamic parameters of the all phases existing in the system were determined.
► The complete phase diagram of the system (Ho–Te) is calculated.