Yanchyts'kyj B. Theoretical study of influence of nitrogen on electronic structure and hyperfine interactions in fcc iron

Numerical algorithm and computer program have been developed to find space symmetry for three dimensional periodic solids that makes treatment of space symmetry more simple and easy. To test the ab-initio method itself, for the Fe4N nitride electronic structure and hyperfine parameters have been calculated and interpreted in details. To investigate hyperfine interactions in nitrogen austenite, two model structures of the Fe8N composition were created in such a way to provide the most important nitrogen surrounding for iron atoms. Calculated electric field gradients (EFG) on the iron nuclei show significant quad-rupole splitting of nuclear levels for iron atoms that are at significant distances (second and third neighbors) from nitrogen. This finding (especially for atoms with nitrogen at the third coordination shell) is not taken into account by modern inter-pretations of experimental M?ssbauer spectra. It is also shown that effects of local atomic distortions change the value of quad-ruple splitting significantly and therefore must be taken into account, as the local atomic distortions take always place in interstitial solid solutions.