Phase Stability, Elastic, Thermo-physical and Electronic Properties of Hexa-(Mo, Cr, W)2C from First-principles Calculations

Phase stability, elastic properties, thermo-physical properties, as well as electronic properties of hexa-(Mo, Cr, W)2C carbides were investigated by first-principles calculations. The results indicated that the Mo8C4, Mo7Cr1C4, Mo7W1C4, Mo6W2C4, and Mo6W1Cr7C4 are stable and the stability follows the sequence: Mo6 W1 Cr1 C4> Mo7 Wi C4 > Mo7 Cr1 C4 > Mo6 W2 C4 > Mo8 C1. Mo6W1Cr1C4 shows the highest stability, deformation resistance and hardness. G/B (shear modulus/bulk modulus) and Poisson's ratio of the stable hexa-(Mo, Cr, W)2C are all larger than 1.75 and 0.26, respectively, which indicates that they are all brittle. The anisotropies are mainly due to the different Vogit shear modulus/Reuss shear modulus; the mechanical anisotropy of Mo7Cr7C4 is the largest, and that of Mo8C4 is the smallest. Moreover, the obtained Debye temperature ΘD and heat capacity Cp indicate that Mo6W2C4 possesses the best thermal conductivity (ΘD = 497.72 K), while Mo7Cr1C4 and Mo6W2C4 possess the largest heat capacity when the temperature is in the range of 0 - 10 K and larger than 10 K, respectively. From the electronic property analysis, the doped Cr and W atoms can not only participate in orbitals hybridization themselves but also enhance the orbitals hybridization between Mo and C atoms, which can reinforce the interatomic interactions.