It was found that data for 1000 to 1350C could be described by:

D (cm2/s) = 6.9 x 10-3 exp[-12.9(kcal/mol)/RT]

K.E.Oberg, L.M.Freidman, W.M.Boorstein, R.A.Rapp: Metallurgical Transactions, 1973, 4[1], 61-7