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 Mo6W1Cr1C4 are stable and the stability follows the sequence：Mo6W1Cr1C4〉Mo7W1C4〉Mo7Cr1C4〉 Mo6W2C4〉 Mo8C4.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 Mo7Cr1C4 is the largest,and that of Mo8C4 is the smallest.Moreover,the obtained Debye temperatureΘDand heat capacity Cpindicate that Mo6W2C4 possesses the best thermal conductivity（ΘD=497.72K）,while Mo7Cr1C4 and Mo6W2C4possess the largest heat capacity when the temperature is in the range of 0-10 Kand 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.