The effects of ordered carbon vacancies on stability and thermo-mechanical properties of VC compared with VC.

The ordered non-stoichiometric VC can form in the VC carbides by the disorder-order phase transformation. The intrusion of ordered carbon vacancies can affect their stability, mechanical, thermal and electronic properties. The relatively thermodynamic stability and mechanical properties at high temperature for the ordered stoichiometric VC and non-stoichiometric VC are investigated in this paper by first-principle calculations combined with the quasi-harmonic approximation. The difference between the properties of VC and VC can be obtained. We find that the VC is thermodynamic more stable than VC, but has weaker elastic heat resistance than VC. Moreover, the minimum thermal conductivity of VC is a little larger than VC and a simple way is proposed to characterize the anisotropy of lattice thermal conductivity based on the Cahill's model.