Understanding the diffusion mechanism of hydrogen in titanium could give fundamental knowledge to reveal the mechanisms of thermo-hydrogen processing of titanium alloys. The diffusion characteristics of hydrogen along the C axis and in the basal plane of α-Ti were studied using the first-principles total-energy pseudo-potential method. For hydrogen diffusion in the basal plane, the calculations show that the indirect octahedral–tetrahedral–octahedral mechanism was energetically more favourable than the direct octahedral–octahedral mechanism and the calculated activation energy of 0.514eV was in good agreement with the experimental data. For hydrogen diffusion along the C axis, the direct octahedral–octahedral mechanism was most favoured and the calculated activation energy was 0.694 eV. The results indicate that there were different mechanisms and anisotropy for hydrogen diffusion along the C axis and in the basal plane of α-Ti.

First-Principles Study of Hydrogen Diffusion in Alpha Ti. X.L.Han, Q.Wang, D.L.Sun, T.Sun, Q.Guo: International Journal of Hydrogen Energy, 2009, 34[9], 3983-7