Structural stability and hydrogen diffusion in TiHx alloys

Structural stability and hydrogen diffusion in TiHx alloys, with x=0–2x=0–2, have been studied by ab initio   total energy calculations. A concentration dependent structural transformation is predicted to occur from FCC (x≤0.5)(x≤0.5) to FCT (0.75≤x≤1.50)(0.75≤x≤1.50) and then again to FCC (1.75≤x≤2.0)(1.75≤x≤2.0). Moreover, a concentration independent hydrogen diffusion behavior is found with activation energies of 0.50 eV in TiH0.75 (along the [110] direction) and 0.54 eV in TiH1.75 (along the [100] direction), respectively. These results are in good agreement with the recent experimental works.