A simple lattice-gas model was used to describe the reaction, of N atoms with the metal lattice, in terms of a net reaction energy of -57kJ/mol. The N diffusion was described by:

D(mm2/s) 1.02 exp[-1339kJ/mol)/RT]

as determined from a thermopiezoic analysis of the initial stages of N absorption,

R.Skomski, J.M.D.Coey: Journal of Applied Physics, 1993, 73[11], 7602-11