Stability and elastic properties of Y-C binary compounds investigated by first principles calculations

The first principles calculations based on density functional theory (DFT) were adopted to investigate the stability, elastic constants, hardness, Debye temperature and mechanical anisotropy properties of Y-C binary compounds. The cohesive energy and formation enthalpy of these compounds indicate that they are thermodynamically stable structures. The elastic parameters C-ij were calculated, and then the bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio sigma were evaluated by Voigt-Reuss-Hill (VRH) approximation. The largest B, G, E values and hardness are ascribed to beta-Y2C3 among all YxCy binary compounds. The hardness of compounds was estimated using a semi empirical hardness theory, and the results showed that hardness for all the calculated compounds was less than 17 GPa. The mechanical anisotropy was characterized by calculating several different anisotropic indexes and factors. The calculated anisotropy factors indicate that the YxCy binary compounds show anisotropic mechanical properties and YC2 is largely shear isotropic. (C) 2013 Elsevier B. V. All rights reserved.