First-principles calculations of the mechanical and electronic properties of Fe–W–C ternary compounds

The mechanical and electronic properties of Fe–W–C (Fe2W2C, Fe3W3C, Fe6W6C and Fe21W2C6) ternary compounds were investigated by first-principles calculations. The cohesive energy and formation enthalpy of these compounds show that they are thermodynamically stable. The elastic constants were calculated by using stress–strain method and the Voigt–Reuss–Hill approximation was applied to estimate the mechanical moduli. The calculated bulk modulus values of Fe2W2C, Fe3W3C, Fe6W6C and Fe21W2C6 are 324.9 GPa, 326.0 GPa, 326.1 GPa and 336.1 GPa, respectively, which are larger than Fe3C and Cr7C3. The surface constructions of Young’s moduli were plotted to indicate the mechanical anisotropy. Using a theoretical method based on the works of Tian, the hardness of the crystal is estimated. Moreover, the chemical bonding in these carbides were evaluated by calculating the density of states and Mulliken analysis. The results indicate that all the bonding behaviors in Fe–W–C ternary compounds are the combinations of metallic and covalent bonds.