The diffusivity of Fe under an H2 pressure of 5GPa was determined, at 1004 to 1301K, by relating the interdiffusion coefficients in single-phase Au/Au-Fe couples by using the Darken-Manning relationship. The value of the coefficient at 1301K, under an H2 pressure of 5GPa, was 3 times that under a pressure of 5GPa; without H2. The former was one tenth of that under a He pressure of 0.1MPa. The temperature dependence of the diffusivity under an H2 pressure of 5GPa could be described (figure 4)by:

D (m2/s) = 7.8 x 10-6 exp[-195(kJ/mol)/RT]

The pre-exponential factor was almost equal to that in He at 0.1MPa, but the activation energy was only 21kJ/mol larger than that observed in He at 0.1MPa.

Y.Yamazaki, Y.Iijima, M.Okada: Philosophical Magazine Letters, 2004, 84[3], 165-74