“Softness” as the structural origin of plasticity in disordered solids: a quantitative insight from machine learning

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  • ReceivedApr 23, 2018
  • AcceptedJun 21, 2018
  • PublishedJul 3, 2018


Funded by

the Research Grant Council(RGC)

with the grant number CityU 11207215 and CityU11209317.


Yang Y acknowledges the research funding from Research Grant Council (RGC) of Hong Kong with the grant number CityU 11207215 and CityU11209317.

Interest statement

The authors declare no conflict of interest.

Contributions statement

Liu X, Li F and Yang Y wrote the paper. All authors contributed to the general discussion.

Author information

Xiaodi Liu obtained his bachelor and master degree from Shandong University, Jinan, China, in 2012 and 2015 respectively. He is currently a PhD student under the supervision of Prof. Yong Yang at the Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China. His research focuses on the creep and relaxation behavior of metallic glasses.

Fucheng Li is currently a PhD candidate at the Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China. He received his bachelor degree and master degree from Central South University, Changsha, China in 2013 and 2016, respectively. His PhD research focuses on the mechanical behavior of both bulk nano-grained metallic glass and metallic-glass based nanostructures.

Yong Yang obtained his bachelor degree in 2001 from Peking University, Beijing, China, and PhD in 2007 from Princeton University, NJ, USA. He is currently a Professor at the Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China. His research focuses on mechanical behavior of structural materials and the high throughput design of alloys, such as metallic glasses and high entropy alloys.


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  • Figure 1

    Variation of interatomic potential and modulus with interatomic distance. (a) U(r) vs. r. r0 is the equilibrium position with the minimum value of U(r). The dash line stands for an approximation by a harmonic oscillator potential at r=r0. (b) E(r) vs. r. The inset shows the distribution of moduli.

  • Figure 2

    Relationship between yield strength (σy) and Young’s modulus (E). (a) A general rule for a variety of disordered solids. (b) Enlarged view of the box in (a), to display the details of metallic glasses [8,28,30,3334,4761].

  • Figure 3

    Illustrations of the mechanisms of the plastic deformation in (a–c) crystalline solids and (d–f) disordered solids. For crystalline solids, red spheres represent the atoms in the extra-half plane, and “⊥” stands for the edge dislocation line. The migration of dislocation generates the plastic strain. For disordered solids, the red spheres stand for the “defect” regions, which grow and coalesce under shear stress, leading to local atomic rearrangements. The percolation through the “matrix” composed by the blue spheres causes overall softening and plastic flow.

  • Figure 4

    The comparison of strength size effect between crystal and non-crystal materials [30,33,34,43,4750,55,6269].


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