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.