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

Abstract

We study the electronic structure, formation energies, and magnetic properties of cementite Fe 3 C doped by 3d and 4d transition metals (TM) by means of first-principles calculations. All TM elements demonstrate a preference for the substitution of the general iron position in Fe 3 C. We predict that early elements (Sc, Ti, V, Cr, Zr, and Nb) stabilize the cementite, while the end elements (Ni, Cu, Pd, and Ag) in the TM series sharply destabilize it. The magnetic properties of impurity atoms are found to depend strongly on their atomic numbers and the trends to ferromagnetic or antiferromagnetic coupling of impurities with Fe atoms in Fe 3 C coincide with the magnetic behavior of these impurities in Fe. The physical reason is a similar location of the Fermi level in the pseudogap of spin-down and almost filled spin-up Fed states in both Fe 3 C and Fe.

Electronic structure and magnetic properties of Fe3C with 2p and 3p impurities

“…The calculations were performed for the Fe12C4 cell (four formula units), where the impurity (B, N, O, Al, Si, P, or S) occupies Fe g , Fe s , or C positions. For Fe 3 C, we obtained the optimized lattice parameters and internal atomic positions to be in good agreement with the experimental data 20–22 and other theoretical estimations 9–13, 15, 23.…”

“…8, where the effect of 3d impurities (Ti, V, Cr, Mn, Co, and Ni) on the chemical bonding was studied within the cluster spin‐restricted approach. Ab initio calculations gave information on the electronic structure and stability of undoped Fe 3 C 9–12 and Fe 3 C alloyed with 3d and 4d transition metals 13–16. The magnetic properties of impurities were found to depend on their atomic numbers and the trends to ferromagnetic or antiferromagnetic coupling of impurities in Fe 3 C coincide with their magnetic behavior in Fe due to the similarity of their electronic structures.…”

First-Principles Calculations on Stabilization of Iron Carbides (Fe3C, Fe5C2, and η-Fe2C) in Steels by Common Alloying Elements

“…The stabilization of a carbide by an alloying element is usually given [20,27] by the change in formation enthalpy of the alloying-element-substituted carbide with respect to the pure carbide as…”

“…In Fe 3 C; when substitution of the alloying elements is considered only on the metal site, all alloying elements prefer to occupy the 8d site. [20,31] When P and S are substituted on the metal sites, it is observed that there is a major reorganization of the nearest neighbor atoms. Fe atoms are observed to move closer to the P and S atoms, both of which have p valence electrons.…”

“…[12] The energetics and electronic structure of impurity substituted cementite have also been the focus of a considerable number of previous studies. [11,[18][19][20][21][22][23][24][25][26][27][28][29][30] The partitioning behavior of alloying elements between cementite and ferrite has been described, [31] and the stabilization of cementite by various alloying elements has been studied. [20][21][22][23][24][25][26][27][28][29][30] In most previous computational work on the stabilization of carbide phases by alloying elements, conclusions were based on enthalpies of formation with respect to the pure carbide phase.…”