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Tension–compression asymmetry in amorphous silicon


Hard and brittle materials usually exhibit a much lower strength when loaded in tension than in compression. However, this common-sense behaviour may not be intrinsic to these materials, but arises from their higher flaw sensitivity to tensile loading. Here, we demonstrate a reversed and unusually pronounced tension–compression asymmetry (tensile strength exceeds compressive strength by a large margin) in submicrometre-sized samples of isotropic amorphous silicon. The abnormal asymmetry in the yield strength and anelasticity originates from the reduction in shear modulus and the densification of the shear-activated configuration under compression, altering the magnitude of the activation energy barrier for elementary shear events in amorphous Si. In situ coupled electrical tests corroborate that compressive strains indeed cause increased atomic coordination (metallization) by transforming some local structures from sp3-bonded semiconducting motifs to more metallic-like sites, lending credence to the mechanism we propose. This finding opens up an unexplored regime of intrinsic tension–compression asymmetry in materials.

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Fig. 1: T-C asymmetry in submicrometre-sized a-Si.
Fig. 2: T-C asymmetry of submicrometre-sized a-Si in the nominally ‘elastic’ regime.
Fig. 3: MD simulations of the T-C asymmetry in a-Si.
Fig. 4: Electrical resistance measured for a-Si under tension versus compression.

Data availability

Source data are provided with this paper. Additional data reported in the Supplementary Information are available from the corresponding authors upon request.

Code availability

The computer codes are available from the corresponding authors upon reasonable request.


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Z.S. and Y.W. acknowledge support from National Natural Science Foundation of China (51902249 and 5203000210), the National Key Research and Development Program of China (no. 2017YFB0702001) and China Postdoctoral Science Foundation (2019M663696). J.D. acknowledges support from National Natural Science Foundation of China (12004294) and National Youth Talents Program. J.L. acknowledges support by the National Science Foundation (DMR-1923976). L.T. acknowledges the Alexander von Humboldt Foundation and the Start-Bridge-Finish Program from International Center for Advanced Studies of Energy Conversion (ICASEC) for financial support. Z.F. thanks A. Bartok-Partay for the help in using the ML-based interatomic potential, and acknowledges the computational resources of the Maryland Advanced Research Computing Center. We thank R. Ritchie and M. Asta for helpful discussions. We thank J. Zhu, S. Yan and D. Zhang at Xi’an Jiaotong University for their assistance in nano dynamic mechanical analysis tests. E.M. and J.D. thank Xi’an Jiaotong University for supporting their work at the Center for Alloy Innovation and Design (CAID).

Author information




E.M., J.L. and Z.S. supervised the project. Y.W. and L.T. carried out the experimental investigations with assistance from M.L., H.L. and Y.Z.; J.D. and Z.F. led the modelling effort. E.M. and Y.W. wrote the paper with input from J.D., Z.F., J.L. and Z.S. All authors contributed to the discussions.

Corresponding authors

Correspondence to En Ma or Ju Li or Zhiwei Shan.

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The authors declare no competing interests.

Additional information

Peer review information Nature Materials thanks Paul McMillan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figures 1-19, Supplementary Notes 1-3, Supplementary Table 1, and additional references 1–17.

Supplementary Video In situ TEM video shows the tension and compression processes of a representative a-Si TC sample.

Source data

Source Data Fig. 1

Statistical Source Data

Source Data Fig. 2

Statistical Source Data

Source Data Fig. 3

Statistical Source Data

Source Data Fig. 4

Statistical Source Data

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Wang, Y., Ding, J., Fan, Z. et al. Tension–compression asymmetry in amorphous silicon. Nat. Mater. (2021).

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