It was found that the data for polycrystalline samples, at 770 to 950C, were described by:

D (cm2/s) = 2.78 x 10-1 exp[-43.39(kcal/mol)/RT]

V.N.Kaigorodov, S.M.Klotsman, A.N.Timofeev, I.S.Trakhtenberg: Fizika Metallov i Metallovedenie, 1968, 25[5], 910-23