Yablonovskyi S. Theoretical investigation of the short range order and the parameters of hyperfine interactions in Fe-N and Fe-C austenites.

Dissertation is dedicated to the theoretical investigation of the nitrogen and carbon atoms distribution in the fcc iron lattice. Electronic structure modelling and hyperfine interaction parameters calculation were carried out with the help of high precision ab-initio FLAPW method. Carbon-carbon pair potentials have been calculated in FCC iron matrix. Monte Carlo modelling has shown that, contrary to nitrogen, carbon atoms are being repulsed by each other and take up the positions at the maximal distance between each other. The calculations of atomic structure and average values of the hyperfine interaction parameters in five ordered Fe32A3 (A = C, N) structures with different interstitial atoms arrangement were performed by FLAPW method to interpret experimental spectra. Mossbauer spectra of the alloys have been calculated on the basis of the results of Monte Carlo modelling of the short range order and calculated parameters of hyperfine interactions.