The mechanical and electronic properties of o-Fe₂C, h-Fe₃C, t-Fe₅C₂, m-Fe₅C₂ and h-Fe₇C₃ compounds: First-principles calculations

The study aims at assessing the elastic and electronic properties of o-Fe₂C, h-Fe₃C, t-Fe₅C₂, m-Fe₅C₂ and h-Fe₇C₃ compounds using first-principles calculations based on the density functional theory. A comprehensive study of elastic constants and moduli shows that five compounds fulfill mechanical and dynamic stability conditions and are ductile. The Young's and shear modulus for o-Fe₂C, h-Fe₃C, t-Fe₅C₂, m-Fe₅C₂ and h-Fe₇C₃ compounds show elastic anisotropy along different directions due to a small or large deviation in shape from the sphere. t-Fe₅C₂ exhibits the largest degree of elastic anisotropy, while h-Fe₃C possesses the smallest elastic anisotropy in five Fe–C compounds. The electronic structures of o-Fe₂C, h-Fe₃C, t-Fe₅C₂, m-Fe₅C₂ and h-Fe₇C₃ compounds including band structure, density of states and Mulliken analysis have been investigated. The results demonstrate that all the considered Fe–C compounds have the ionic, covalent and metallic chemical bonds.