Theoretical study on the stability, elasticity, hardness and electronic structures of W-C binary compounds

The ground state properties of W-C binary compounds (h-WC, c-WC, α-W2C, β-W2C, γ-W2C, ɛ-W2C) are studied in this paper by using first-principles calculations. Formation enthalpy and cohesive energy for each phase are calculated. The calculated elastic constants satisfy the Born-Huang's stability criterion, indicating all studied compounds are mechanically stable. All W-C compounds studied in this paper exhibit larger bulk modulus values than many other binary types of carbide such as Fe3C, Cr7C3, Cr3C, and TiC. Using a theoretical method based on the works of Šimůnek, the hardness of the crystal is estimated. The electronic structures of these compounds are calculated and discussed. Stoner's polarization theory for itinerant magnetism is applied to explain the observed paramagnetic behavior of the compounds. Moreover, the heat capacity is also calculated for each compound based on the knowledge of the elasticity and Debye temperature.