Fe X (X = B, N) binary compounds: First-principles calculations of electronic structures, theoretic hardness and magnetic properties

• Published in: Journal of magnetism and magnetic materials Vol. 451; pp. 761 - 769
• Main Authors: Hui, Liangliang, Xie, Zhongjing, Li, Chunmei, Chen, Zhi-Qian
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier BV 01.04.2018
• Subjects: Antiferromagnetism; Bonding strength; Borides; Boron; Covalent bonds; Cubic lattice; Electromagnetism; Empirical analysis; Enthalpy; First principles; Hardness; Interstitial compounds; Iron compounds; Iron nitride; Lattice parameters; Magnetic fields; Magnetic moments; Magnetic properties; Mathematical analysis; Microhardness; Microstructure
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2017.12.011

The first-principles calculations are implemented to investigate the electronic structures, theoretic hardness and magnetic properties of iron borides and nitrides with four different crystal systems containing hexagonal (FeB2, ε-Fe3N), tetragonal (Fe2B, α″-Fe16N2), orthorhombic (α-FeB, θ-Fe3B, ζ-Fe2N), and cubic (zb-FeN, rs-FeN, γ′-Fe4N, γ-Fe23B6) phase. The calculated lattice parameters using RPBE meet well with the experimental results. The cohesive energy and formation enthalpy values indicate the FeX (X = B, N) binary compounds are thermodynamically stable. Meanwhile, the h-FeB2 is most difficult phase for experimental synthesis among these interstitial compounds. Moreover, magnetic properties are discussed and show that the mean magnetic moments of o-Fe3B and c-Fe23B6 with the values of 2.227 μB and 2.256 μB per iron atom are approaching to that of pure iron (2.32 μB) while the c-Fe4N and t-Fe16N2 with the values of 2.51 and 2.48 μB are beyond that of pure α-Fe. The c-FeN phase shows nonmagnetic in zb-style while rs-type shows antiferromagnetic with a value of 2.52 μB. Furthermore, the average bonding length and Mulliken population combined with electronic structures are also analysed in this paper which provide that strong Fe―X and X―X covalent bonds are responsible for high hardness. Finally, the theoretic hardness of X―X, Fe―X and Fe―Fe bonds is predicted by semi empirical hardness theory.