Ordering Effects and Hyperfine Interactions in Fe-N Austenites

Abstract

Using the high accurate ab-initio FLAPW method and the cluster expansion technique, interatomic N-N interactions for Fe-N austenite were calculated. The interactions were used for calculation of temperature dependence of the short range order for Fe₁₀ N austenite. For two model structures with different nitrogen distributions, the hyperfine interactions were calculated. It was revealed, that EFG might be nonzero on nuclei even for Fe atoms that do not have nitrogen atoms at the first coordination shell. This finding has to be considered for interpretation of Mössbauer spectra of austenite Fe-N.