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Published January 26, 2022 | Supplemental Material
Journal Article Open

Deformation and Failure Mechanisms of Thermoelectric Type-I Clathrate Ba₈Au₆Ge₄₀

Abstract

Type-I clathrate Ba₈Au₆Ge₄₀, possessing an interesting structure stacked by polyhedrons, is a potential "phonon-glass, electron-crystal" thermoelectric material. However, the mechanical properties of Ba₈Au₆Ge₄₀ vital for industrial applications have not been clarified. Here, we report the first density functional theory calculations of the intrinsic mechanical properties of thermoelectric clathrate Ba₈Au₆Ge₄₀. Among the different loading directions, the {110}/⟨001⟩ shearing and ⟨110⟩ tension are the weakest, with strengths of 4.51 and 6.64 GPa, respectively. Under {110}/⟨001⟩ shearing, the Ge–Ge bonds undergo significant stretching and twisting, leading to a severe distortion of the tetrakaidecahedral cage, giving rise to the fast softening of the flank Au–Ge bonds. At a strain of 0.2655, the Au–Ge bonds suddenly break, resulting in the collapse of the cage and the failure of the material. Under a ⟨110⟩ tension, the stretching of the Ge–Ge bonds keeps accelerating the softening of the Au–Ge bonds in the top/bottom hexagons, which releases the stress and disables the structure. The Au–Ge bonds are more rigid, contributing two-thirds of the structural deformation resistance. This work provides a new insight to understand the failure mechanisms of type-I clathrates with varied framework constitutions, which should help inform the design of robust thermoelectric clathrate materials.

Additional Information

© 2022 American Chemical Society. Received: November 23, 2021; Accepted: January 4, 2022; Published: January 12, 2022. This work was supported by the National Natural Science Foundation of China (nos. 52022074; 92163119, and 92163215), the Hubei Provincial Natural Science Foundation of China (2020CFB202), and the Fundamental Research Funds for the Central Universities (WUT: 2021III058). S.M. is thankful for the support by the Supercomputer Simulation Laboratory of South Ural State University. WAG thanks the US Office of Naval Research (ONR N00014-19-1-2081) for support. The authors declare no competing financial interest.

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Created:
August 22, 2023
Modified:
October 23, 2023