Measurements of the H self-diffusion coefficient in the a'-phase of the Nb-H system were performed by means of nuclear magnetic resonance spin-echo pulsed-magnetic field-gradient techniques at 90 to 243C. The data for NbH0.6, at temperatures above 100C, could be described by:

D (cm2/s) = 6.6 x 10-4 exp[-0.165(eV)/kT]

R.M.Cotts, O.J.Zogal: Physical Review B 1975, 11[7], 2443-6