A pulsed-field gradient nuclear magnetic resonance spin echo technique was used to measure the diffusivities in NbHx. It was found that the activation energy increased with increasing H concentration, whereas the pre-exponential factor was not markedly concentration-dependent:

NbH0.10:     D (cm2/s) = 3.2 x 10-4 exp[-0.115(eV)/kT]

NbH0.33:     D (cm2/s) = 4.9 x 10-4 exp[-0.142(eV)/kT]

NbH0.55:     D (cm2/s) = 1.0 x 10-3 exp[-0.168(eV)/kT]

NbH0.70:     D (cm2/s) = 7.2 x 10-4 exp[-0.174(eV)/kT]

NbH0.89:     D (cm2/s) = 5.6 x 10-4 exp[-0.164(eV)/kT]

The results were not consistent with the random occupation of tetrahedral sites, and it was suggested that repulsive interactions existed between H atoms on nearest-neighbor sites.

P.E.Mauger, W.D.Williams, R.M.Cotts: Journal of the Physics and Chemistry of Solids, 1981, 42[9], 821-6

The best linear fits to the solute diffusion data ([1015] to [1019], [1021] to [1030]) yield:

H: Ln[Do] = 0.55E – 9.4 (R2 = 0.92); N: Ln[Do] = 0.23E – 12.2 (R2 = 0.73);

Nb: Ln[Do] = 0.20E – 19.4 (R2 = 0.94)