It was found that the data for 63Ni at 900 to 1200C could be described by:

polycrystalline:     D (cm2/s) = 2.22 x 100 exp[-69.2(kcal/mol)/RT]

monocrystalline:     D (cm2/s) = 2.59 x 100 exp[-70.1(kcal/mol)/RT]

I.G.Ivantsov: Fizika Metallov i Metallovedenie, 1966, 22[5], 725-9