Determining ideal strength and failure mechanism of thermoelectric CuInTe_2 through quantum mechanics

Abstract

CuInTe_2 is recognized as a promising thermoelectric material in the moderate temperature range, but its mechanical properties important for engineering applications remain unexplored so far. Herein, we applied quantum mechanics (QM) to investigate such intrinsic mechanical properties such as ideal strength and failure mechanism along with pure shear, uniaxial tension, and biaxial shear deformations. We found that the ideal shear strength of CuInTe_2 is 2.43 GPa along the (221)[11−1] slip system, which is much lower than its ideal tensile strength of 4.88 GPa along [1−10] in tension, suggesting that slipping along (221)[11−1] is the most likely activated failure mode under pressure. Shear induced failure of CuInTe_2 arises from softening and breakage of the covalent In–Te bond. However, tensile failure arises from breakage of the Cu–Te bond. Under biaxial shear load, compression leads to shrinking of the In–Te bond and consequent buckling of the In–Te hexagonal framework. We also found that the ideal strength of CuInTe_2 is relatively low among important thermoelectric materials, indicating that it is necessary to enhance the mechanical properties for commercial applications of CuInTe_2.