Effect of Sc, V, Zr, and Hf doping on the mechanical properties of TiB3 under high pressure

The influence of 3d-Sc, 3d-V, 4d-Zr, and 5d-Hf doping on the mechanical properties of the TiB3 has been investigated in the pressure range of 0–200 GPa by using first-principles calculations. On the basis of verifying the structure stability of the TiB3, its doping is studied. By calculating the elastic constants and phonon dispersion, it is confirmed that the doped structures satisfy the mechanical and dynamic stability. And the mechanical properties of the doped structures are calculated. It is found that the toughness of the Ti0.75V0.25B3, Ti0.75Zr0.25B3 and Ti0.75Hf0.25B3 increases, and the elastic isotropy of the Ti0.75Zr0.25B3 and Ti0.75Hf0.25B3 increases, while the Vickers hardness of the Ti0.75TM0.25B3 (TM = Sc, V, Zr, and Hf) decreases except for the Ti0.75Sc0.25B3. The analysis of the density of states, electronic local functions and bond length implies that the enhancement of mechanical properties of the Ti0.75Sc0.25B3 is mainly due to the enhancement of Sc-B covalent bond strength, and the weakening of mechanical properties of the Ti0.75V0.25B3 is mainly due to the weakening of B-B and V-B covalent bond strength. And the weakening of B-B covalent bond strength leads to the decrease of mechanical properties of the Ti0.75Zr0.25B3 and Ti0.75Hf0.25B3.