The diffusivity was determined in monocrystalline Ni by using a permeation time-lag technique at 200 to 420C and 77 to 478torr. It was found that  the results obeyed:

D (cm2/s) = 5.22 x 10-3 exp[-9.56(kcal/g-atom)/RT]

Diffusion and Solubility of Hydrogen in Single Crystals of Nickel and Nickel-Vanadium Alloy. Y.Ebisuzaki, W.J.Kass, M.O'Keeffe: Journal of Chemical Physics, 1967, 46[4], 1378-81