Electronic structure and magnetic properties of the α and γ phases of iron, their solutions with carbon, and cementite

Electronic structure and magnetic properties of Fe3C with 3d and 4d impurities

“…It should be noted that the covalent bonding between iron and carbon atoms is not strong as demonstrated by the low density of Fe 3d states in the energy interval from -8 to -4 eV below the Fermi level (where the bonding C2p states are placed) and the small contribution of the C2p states in the range from -4 eV to E F . Our estimations [14] showed, that the contributions in the cohesive energy of Fe 3 C from the Fe-Fe, Fe-C and C-C bonds are 62, 38 and <1%, respectively. Now we consider the changes in the local d-DOS of impurities at their preferable sites in Fe 3 C (Figs.…”

“…It is well known [33,34], that the carbide-forming activity of 3d atoms (their ability to form the strong covalent M-C bonds) sharply decreases going to the end TM's. The Fe-C bonds were shown [14] to be weak in unalloyed Fe 3 C and the appearance of additional M-C bonds leads to the lowering of the total energy for (FeM) 3 C alloys with carbide-forming elements in the earlier TM's (Sc, Ti, V, Cr, and Nb). These reasons also may be used for the interpretation of substitution site preference.…”

“…The general sites were found experimentally as the preferred site occupation for Cr and Mn additions in the cementite [36]. found with positive (∆H = 0.8 eV/f.u., [14]) and negative (∆H = -3.6 eV/f.u., [18]) values of ∆H. The value obtained in our work is in agreement with the experimental finding ∆H f 0 = +4.7 ÷ 6.3 kJ/mole (or 0.05 ÷ 0.07 eV/f.u.)…”

“…A number of studies of the electronic band structure and magnetic behavior of unalloyed cementite have been performed: Haglund et al [13] using the LMTO-ASA method estimated the atomic magnetic moments, the electron-phonon coupling parameter, cohesive energy, electronic heat capacity; chemical bonding and the effects of carbon atom locations and non-stoichiometry on the electronic and magnetic states of Fe 3 C were investigated by Medvedeva et al [14][15][16] by means of the full-potential LMTO; the pseudopotential-based density functional theory was used by Vocadlo et al [17] and Chiou et al [18] to determine the equation of state and investigate the surfaces of Fe 3 C, respectively; metamagnetic transition and magnetovolume anomaly in Fe 3 C were investigated by Khmelevskyi et al [19]. However, the only attempt has been made to explain the effect of 3d impurities (Ti, V, Cr, Mn, Co, and Ni) on the chemical bonding of cementite by the cluster discretevariational approach [12].…”

Structure and Magnetic Properties of the Nanocrystalline (Mechanically Alloyed) and Annealed Cementite

“…The calculation results are of special importance, in which comparison between the C atoms in the prismatic and octahedral interstices is carried out [30,31]. The calculation results are of special importance, in which comparison between the C atoms in the prismatic and octahedral interstices is carried out [30,31].…”