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

The structure, elastic properties and electronic structure of VC and V4C3 have been studied by the first-principles pseudopotential plane-wave method based on density functional theory. Compared with VC, V4C3 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 V4C3 were calculated. The higher shear modulus of VC is due to the differences of DOS for VC and V4C3. The overlap populations of the V-C bonds in VC and V4C3 were analyzed and the hardnesses of VC and V4C3 were calculated. The calculated hardness of V4C3 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. (c) 2008 Elsevier B. V. All rights reserved.