<i>In Situ</i> Atomic-Scale Quantitative Evidence of Plastic Activities Resulting in Reparable Deformation in Ultrasmall-Sized Ag Nanocrystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 38010413.
- Also identified by DOI 10.1021/acsnano.3c05808.
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Abstract
Permanent structural changes in pure metals that are caused by plastic activity are normally irreparable after unloading. Because of the lack of experimental evidence, it is unclear whether the plastic activity can be repaired as the size of the pure metals decreases to several nanometers; it is also unclear how the metals accommodate the plastic deformation. In this study, the <i>in situ</i> atomic-scale loading and unloading of ∼2 nm Ag nanocrystals was investigated, and three modes of plastic deformation were observed: (i) the phase transition from the face-centered cubic (fcc) phase to the hexagonal close-packed (hcp) phase, (ii) stacking faults, and (iii) deformation twin nucleation. We show that all three modes resulted in structural changes that were reparable, and their generation and restoration during loading and unloading were observed <i>in situ</i>. We discovered that the deformation modes of nanosized metals can be predicted from the ratio of the energy barriers of the fcc-hcp phase transition (Δγ<sub>H</sub>) and the deformation twin nucleation (Δγ<sub>T</sub>), which differ from those of the theoretical modes of relatively large-sized metals. The proposed Δγ<sub>H</sub>/Δγ<sub>T</sub> criterion provides insights into the deformation mechanism of nanometals.