A thermodynamic modeling of the Gd–Tl system

The phase equilibria and thermodynamic properties of the Gd–Tl system were optimized using the CALPHAD (CALculation of PHAse Diagram) technique. In the present work, the excess Gibbs energies of the liquid, bcc and hcp solution phases were modeled using the polynomial temperature dependence and Kaptay equation. The intermetallic compounds Gd2Tl, Gd3Tl5 and GdTl3 were treated as stoichiometric compounds. The intermetallic compound Gd5Tl3, which had a homogeneity range, was treated with a sublattice model (Gd,Tl)5Tl3. A sublattice model (Gd,Tl)0.5(Gd,Tl)0.5 was applied to describe the compound GdTl in order to cope with the order–disorder transition between GdTl with CsCl-type structure (B2) and body-centered cubic solution (A2) in the Gd–Tl system. Two sets of self-consistent thermodynamic parameters were obtained.