Mechanical and electronic properties of A1−xBxHy (A and B=Ti, Zr, Hf) hydride alloys: A first-principles study

•β-Phase MH1.5[100] (M=Ti, Zr, Hf) are more stable than other possible structures.•Increasing H concentration in MHy induces the tetragonal distortion.•Ti0.75Hf0.25H1.5 and Zr0.75Hf0.25H1.5 exhibit the highest mechanical stability.•Systems considered in the present work are anisotropic and show a ductile behavior.•The electronic conductivity of A1−xBxHy exhibits metallic character. Using ab initio calculations, we investigated the mechanical and electronic properties of Ti1−xHfxHy, Ti1−xZrxHy and Zr1−xHfxTHy (x=0, 0.25, 0.5, 0.75, 1; y=1.5, 1.75, 2). The calculated results in binary hydrides show that the β-phase MH1.5[100] (M=Ti, Zr, Hf) are more stable than other possible structures. At the Fermi level, the density of states for metal d state increases with increasing the H concentration in MHy (y ranged from 1.5 to 2), which leads to the instability of their fcc structures and induces the tetragonal distortion. Ti0.75Hf0.25H1.5 and Zr0.25Hf0.75H1.5 exhibit the highest mechanical stability, while Ti0.25Zr0.75H1.5 has the lowest mechanical stability among the corresponding ternary systems considered. Moreover, the systems studied in the present work are all anisotropic and show a ductile behavior. The tetragonal distortion in Ti1−xHfxH1.5, Ti1−xZrxH1.5 and Zr1−xHfxH1.5 is not observed, retaining their fcc structures. The electronic structure of A1−xBxHy (A and B=Ti, Hf, Zr) exhibits metallic character.