Ab initio calculations of the mechanical and acoustic properties of Ti2-based Heusler alloys under pressures

Abstract

The mechanical and acoustic properties of Ti2NiZ (Z = Al, Ga and In) Heusler alloys under different pressures were studied based on the second- and third-order elastic constants obtained by the ab initio calculations combined with homogeneous deformation theory. The results showed that the mechanical stability is reduced while the ductility is improved with increasing pressure for all three alloys. As the pressure increases, the acoustic velocities of these alloys increase except for the transverse acoustic velocities in ⟨110⟩ direction of Ti2NiGa and Ti2NiIn. The Debye temperature and minimum thermal conductivity were also predicted in terms of the obtained acoustic velocities, which increase with increasing pressure for all three alloys. The calculated lattice constants, band gaps and second-order elastic constants were in agreement with the available theoretical values.