The recovery of excess D which was dissolved in Ni was studied by means of liquid-H quenching and electrical resistivity measurements. The diffusion of D was found to be described by:

D (cm2/s) = 3.18 x 10-3 exp[-9220/RT]

at temperatures of between 220 and 340K. A study of these and other results showed that the pre-exponential factor for H diffusion was lower than that for D diffusion. The same relationship was true of the activation energies. This appeared to be abnormal from the standpoint of classical diffusion theory. The ratio, DH/DD, was always greater than unity, and increased with decreasing temperature. It differed from simple extrapolations of the results of other investigators, in which the ratio fell below unity with decreasing temperature.

Diffusion of Deuterium and Isotope Effect in Nickel. K.Yamakawa: Journal of the Physical Society of Japan, 1979, 47[1], 114-21