In situ atomic-scale observation of continuous and reversible lattice deformation beyond the elastic limit
Lihua WangPan LiuPengfei GuanMingjie YangJia‐Lin SunYongqiang ChengAkihiko HirataZe ZhangE. MaMingwei ChenXiaodong Han
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Abstract:
The elastic strain sustainable in crystal lattices is usually limited by the onset of inelastic yielding mediated by discrete dislocation activity, displacive deformation twinning and stress-induced phase transformations, or fracture associated with flaws. Here we report a continuous and gradual lattice deformation in bending nickel nanowires to a reversible shear strain as high as 34.6%, which is approximately four times that of the theoretical elastic strain limit for unconstrained loading. The functioning deformation mechanism was revealed on the atomic scale by an in situ nanowire bending experiments inside a transmission electron microscope. The complete continuous lattice straining process of crystals has been witnessed in its entirety for the straining path, which starts from the face-centred cubic lattice, transitions through the orthogonal path to reach a body-centred tetragonal structure and finally to a re-oriented face-centred cubic structure. In bulk materials crystal lattices typically have a limited resistance to elastic strain, beyond which yielding and plastic deformation occur. Here, usingin situtransmission electron microscopy, a continuous elastic lattice deformation is observed in nickel nanowires, up to a strain of 34.6%.Keywords:
Tetragonal crystal system
Atomic units
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Cubic crystal system
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Crystallization of noble metal atoms usually leads to the highly symmetric face-centred cubic phase that represents the thermodynamically stable structure. Introducing defective microstructures into a metal crystal lattice may induce distortions to form non-face-centered cubic phases when the lateral dimensions of objects decrease down to nanometre scale. However, stable non-face-centered cubic phases have not been reported in noble metal nanoparticles. Here we report that a stable body-centred tetragonal phase is observed in silver nanoparticles with fivefold twinning even at ambient conditions. The body-centered tetragonal phase originates from the distortion of cubic silver lattices due to internal strains in the twinned nanoparticles. The lattice distortion in the centre of such a nanoparticle is larger than that in the surfaces, indicating that the nanoparticle is composed of a highly strained core encapsulated in a less-strained sheath that helps stabilize the strained core. Crystallization of noble metal atoms usually leads to the thermodynamically stable face-centred cubic phase. Sunet al. show that internal strain in silver nanoparticles leads to lattice distortion and a stable body-centred tetragonal phase.
Tetragonal crystal system
Cubic crystal system
Noble metal
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