It was recalled that the distribution of C and N atoms in the octahedral interstitial sites of the face-centered cubic austenite phases of these alloys was unclear. Mössbauer experiments, the quasi-chemical approximation, the hard-blocking excluded-sites model, electron charge calculations and Monte Carlo simulations were used to increase its understanding. Mössbauer spectra were analyzed by using models which assumed an ordered or random distribution of the interstitial atoms in the interstices around an Fe atom. The data were compared as a function of the fraction of occupied sites, and striking differences between the Fe-N and Fe-C alloys were noted.

Arrangements of Interstitial Atoms in FCC Fe–C and Fe–N Solid Solutions. J.Desimoni: Hyperfine Interactions, 2004, 156-157[1-4], 505-21