First-principles study of the lattice vibration, elastic anisotropy and thermodynamical properties of Tantalum Silicide with the different crystal structures

Abstract

TaSi2 is the ultra-high-temperature ceramic material, the intrinsic brittleness hinders its high temperature applications. We design five possible structures (Cmcm-type, FdddZ-type, I4/mmm-type and P6222-type and P4332-type structures) by means of first-principles calculations. The structural influence on their lattice vibration, mechanical, electronic and thermal properties were investigated. Except for P4332-type structure, the rest of potential structures are structurally stable. Meanwhile, the I4/mmm-type structure presents the largest hardness among the four structures. As for the anisotropic features, P6222-type structure TaSi2 can be the potential isotropic material and Cmcm-type structure has the relatively obvious anisotropic features in consideration of the anisotropic indexes and the directional dependence of Young's modulus. The electron properties for the four possible structures were discussed by the PDOS and TDOS curves. The thermal behavior of Cmcm-type and FdddZ-type structures are similar in results, and exhibits the nearly coincident curves of the Debye temperature, heat capacity, entropy and enthalpy.