The diffusion behaviour of hydrogen, deuterium and tritium from the (110) surface into the bulk, and in the bulk, was investigated using first-principles calculations combined with simplified models. The diffusion energy barrier, from the (110) surface to the sub-surface, was shown to be 1.87eV; with a much reduced barrier (0.06eV) for the reverse diffusion process. When H entered the bulk, its diffusion energy barrier - with quantum correction - was 0.19eV. In terms of the diffusion theory of Wert and Zener, the pre-exponential factor of H was calculated to be 1.57 x 10-7m2/s, and was in quantitative agreement with the experimental value (4.1 x 10-7m2/s). According to the mass-dependence of the H isotope effect, the pre-exponential factors of D and T were estimated to be 1.11 x 10-7 and 0.91 x 10-7m2/s, respectively.

First-Principles Investigation of Diffusion Behaviours of H Isotopes: from W(110) Surface into Bulk and in Bulk W. Y.L.Liu, W.Lu, A.Y.Gao, L.J.Gui, Y.Zhang: Chinese Physics B, 2012, 21[12], 126103

Table 194

Diffusivity of H in W