Anisotropic mechanical properties and electronic structures of transition metal carbonitrides M_2CN (M=V/Ti/Ta, Nb, Hf and Zr) by first-principles calculations

摘要

Transition metal carbonitrides play an important role in high-temperature structural ceramics, igh-temperature coatings and alloy reinforcements. In this paper, we have searched for more than a dozen compounds of the type M_xC_yN_z, with the special focus on M_2CN compounds. The electronic structure and mechanical properties of transition-metal carbonitrides M_2CN (M = V, Ti, Ta, Nb, Hf and Zr) are investigated by the first-principle calculations based on the density functional theory. The stability of ternary compounds M_2CN is evaluated by calculating cohesive energy, formation energy and phonon dispersion spectrum. Electronic structures and chemical bonding characteristics are analyzed by the density of states and Mulliken population analysis. The mechanical properties, such as bulk, shear, Young's modulus, hardness and Poisson's ratio, are obtained, the modulus of M_2CN is generally higher than that of other carbonitrides. The anisotropic mechanical properties of M_2CN are interpreted, anisotropic index and three-dimensional surface contours show that Ti_2CN has the weakest elastic anisotropy. The simple mixed values H_M, B_M, G_M and E_M are calculated and are compared with the earlier calculated and experimental values.