Explorations of elastic anisotropies and thermal properties of the hexagonal TMSi2 (TM = Cr, Mo, W) silicides from first-principles calculations

Abstract

In this study, the first-principles (DFT) is used to explore the structural properties, elastic anisotropies, and thermal properties of hexagonal TMSi2 (TM = Cr, Mo, W) silicides. The elastic properties of single-crystal and poly-crystal are acquired by using Voigt-Reuss-Hill approximations method. The hardness of TMSi2 silicides were calculated from the bulk B and shear moduli G; In addition, the results show that hexagonal TMSi2 silicide is not potentially super-hard materials. Meanwhile, in terms of their Poisson’s ratio, GH/BH and Cauchy pressures, TMSi2 silicides are brittle material. Elastic anisotropies of TMSi2 silicides are measured by using anisotropy index of elastic properties, 3D surface constructions of elastic moduli and their two-dimensional planar projections were used to indicate the elastic anisotropies of these TMSi2 silicides. The sequence of elastic anisotropy follows as WSi2 > MoSi2 > CrSi2. Finally, the sound velocities, Debye temperatures, thermal conductivity and their anisotropies of these silicides were discussed, the sound velocities and Debye temperature of these TMSi2 silicides are anisotropic in the [100] and [001] directions.