Interaction and arrangement of nitrogen atoms in FCC γ-iron

A Mossbauer effect measurement of 57 Fe has been performed for the Fe-N austenite in order to study the interaction between nitrogen atoms and the distribution among the octahedral sites of the FCC lattice. The spectrum for Fe-N austenite is decomposed into one singlet gamma 0 and two sets of doublets gamma 1 and gamma 2 which are identified as being caused by iron atoms with different configurations of nitrogen atoms at the nearest-neighbour sites. The fractional intensities for the three components are precisely determined by taking into account the effect of the absorber thickness. It is concluded from the analysis that the interaction between the first-nearest-neighbour nitrogen atoms is strongly repulsive and that between the second nearest nitrogen is weakly attractive.