The structural, magnetic, electronic, and mechanical properties of orthogonal/hexagonal M7C3 (M = Fe and Cr) carbides from first-principles calculations

• Published in: Vacuum 2022-09, Vol.203, Article 111175
• Main Authors: Zhang, D., Hou, T.P., Liang, X., Zheng, P., Zheng, Y.H., Lin, H.F., Wu, K.M.
• Format: Article
• Language: English
• Subjects: Electronic structure; First-principles calculations; M7C3 carbide; Mechanical properties
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/j.vacuum.2022.111175

First-principles calculations were performed to investigate the structural, magnetic, electronic, and mechanical properties of orthogonal (o-)/hexagonal (h-) M7C3 (M = Fe and Cr) carbides. The o/h-M7C3 structural framework is formed by a 9-vertex Bernal polyhedron (triplet with C-prisms) combined with tetrahedra and octahedra attached to its free triangular faces. The total magnetic properties of the M7C3 carbide arise from the Wyckoff sites of Fe and Cr atom and Fe - (Fe, Cr or C) bond length. M7C3 carbides have the characteristics of covalent, metallic and ionic bonds. Cr substitution causes the reinforcement of the covalent bond of Fe–Cr. Fe3Cr4C3 has superior mechanical properties with higher hardness and strength, which indicates the probability of the excellent wear resistance of high chromium cast iron. This investigation provides a theoretical basis for obtaining the excellent physical properties of Fe-based materials. •M7C3 framework is formed by tetrahedra, octahedra and a 9-vertex Bernal polyhedron.•The Wyckoff sites of metal atoms and Fe–C bond length affect the magnetism of M7C3.•The substitution of Cr increases the strength of the Fe–Cr covalent bonds.•The Fe3Cr4C3 has the priority to the needs of excellent mechanical properties.