Structural, electronic and magnetic properties of Fe20Cr6Mn6 austenitic alloys with interstitial carbon and nitrogen atoms from density functional theory

Based on a 32-atom supercell system, the structural, electronic and magnetic properties of Fe20Cr6Mn6 alloys are calculated and analyzed using first-principles calculations. The effects of interstitial atoms (N and C) on the properties of Fe20Cr6Mn6 alloys are also discussed. In this 32-atom supercell system with an octahedral interstice in the center, there are four different atomic sites occupied by metal atoms (Fe, Cr and Mn). According to the differences of metal atoms at the different atomic sites, the Fe(20)Cr(6)Mn(6 )alloys have been defined as two structural models. Interstitial atoms (N or C) change the phase stability of Fe20Cr6Mn6 alloys. The supercell volumes increase linearly with the content of N (C) in the supercells for each alloy system. The bond lengths of Mn-C/N or Cr-C/N in the octahedral interstice, not as the supercell volume, do not increase linearly with the content of N (C). The spin moments of the Fe20Cr6Mn6 alloys are very small and the magnetic moments of I-Mn-Cx/Nx alloys and I-Cr-Cx/Nx alloys increase slightly. In Fe20Cr6Mn6 alloys, the electrons transfer from Cr atoms to Fe and Mn atoms, and the ability to gain and lose electrons of metal atoms is changed by the addition of C or N atoms. There is an atomic attraction between metal atoms and C or N atoms from bond population analyses.