The migration of H was investigated, by means of quasi-elastic neutron scattering, at 165 to 300K. A transition from a high-temperature activation energy of 0.106eV, to a low-temperature activation energy of 0.068eV, was observed in this region. The value of the low-temperature activation energy was confirmed by neutron scattering experiments. Below 250K, the results of scattering experiments yielded the relationship:

D (cm2/s) = 1.2 x 10-4 exp[-0.069(eV)/kT]

D.Richter, B.Alefeld, A.Heidemann, N.Wakabayashi: Journal of Physics F, 1977, 7[4], 569-74