Vacancy-induced mechanical and thermodynamic properties of B2-RuAl

We apply the first-principles calculations to investigate the correlation between vacancy and the overall performances of RuAl. Three possible vacancies: Al-va, Ru-va and Ru-Al-va are considered. Al-va vacancy is more thermodynamic stability than that of Ru-va and Ru-Al-va vacancies. Al-va and Ru-Al-va vacancies improve the ductility of RuAl. However, Ru-va vacancy weakens the ductility. The calculated electronic structure shows that the removed atom weakens the localized hybridization between atoms, and forms the weak Ru-Al bond along the shear direction. Finally, we predict that these vacancies improve the heat capacity of RuAl due to the vibration of the removed atom.