First-principles study on the mechanical properties of vanadium carbides VC and V4C3

Abstract The structure, elastic properties and electronic structure of VC and V 4 C 3 have been studied by the first-principles pseudopotential plane-wave method based on density functional theory. Compared with VC, V 4 C 3 has lower values of 13.3%, 19.2% and 17.7% in bulk modulus, shear modulus and Young modulus, respectively. The total density of states (DOS) of VC and V 4 C 3 were calculated. The higher shear modulus of VC is due to the differences of DOS for VC and V 4 C 3 . The overlap populations of the V–C bonds in VC and V 4 C 3 were analyzed and the hardnesses of VC and V 4 C 3 were calculated. The calculated hardness of V 4 C 3 is 15.8 GPa, which is lower than that of VC. The calculated hardness of VC is 28.5 GPa, which matches fairly the experimental one.