The T was introduced into the samples by using a nuclear reaction method in order to avoid surface effects. It was found that the data could be described:

D (cm2/s) = 2.1 x 10-3 exp[-11.1(kcal/mol)/RT]

at 133 to 415C.

W.Kunz, H.Münzel, U.Helfrich, H.Horneff: Zeitschrift für Metallkunde, 1983, 74[5], 289-93