The diffusivity was determined by using a serial sectioning technique in which the concentrations were deduced from the melting points of the slices. The data for 217 to 320C could be described by:

D (cm2/s) = 1.1 x 10-2 exp[-10.1(kcal/mol)/RT]

H.B.Vanfleet: Physical Review B, 1980, 21[10], 4337-9