Thermodynamics assessment of the Erbium-Ruthenium system by combining the Ab-initio and CALPHAD methods

In the present study, the erbium-ruthenium system was optimised using the CALPHAD approach. The thermodynamic properties and the phase diagram were evaluated. The enthalpies of formation of the intermetallic compounds for the binary system Er-Ru were calculated by ab- initio methods. The liquid phase was treated with the exponential model, while a solution model was applied to represent the HCP (Er, Ru) solid solution. The five intermetallic compounds Er3Ru, Er5Ru2, Er3Ru2, ErRu2, and Er44Ru25 were considered as stoichiometric compounds. The calculations are in good agreement with the phase diagram information and experimental thermodynamic values documented in the literature.