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Abstract Ultrahigh surface-to-volume ratio in nanoscale materials, could dramatically facilitate mass transport, leading to surface-mediated diffusion similar to Coble-type creep in polycrystalline materials. Unfortunately, the Coble creep is just a conceptual model, and the associated physical mechanisms of mass transport have never been revealed at atomic scale. Akin to the ambiguities in Coble creep, atomic surface diffusion in nanoscale crystals remains largely unclear, especially when mediating yielding and plastic flow. Here, by using in situ nanomechanical testing under high-resolution transmission electron microscope, we find that the diffusion-assisted dislocation nucleation induces the transition from a normal to an inverse Hall-Petch-like relation of the strength-size dependence and the surface-creep leads to the abnormal softening in flow stress with the reduction in size of nanoscale silver, contrary to the classical “alternating dislocation starvation” behavior in nanoscale platinum. This work provides insights into the atomic-scale mechanisms of diffusion-mediated deformation in nanoscale materials, and impact on the design for ultrasmall-sized nanomechanical devices.
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This content will become publicly available on January 6, 2026
Unraveling Photoplasticity in ZnS: Enhanced Peierls Stress under Photoexcitation using Machine Learning Potentials
Photoplasticity, the light-induced alteration of mechanical properties in semiconductors, is crucial for the development of advanced optoelectronic devices and the understanding of semiconductor mechanics. Despite progress in understanding this phenomenon, atomic-scale mechanisms, particularly under photoexcitation, remain complex and are partially understood. Here, we introduce a new computational framework combining constrained Density Functional Theory (CDFT) with machine learning potential (MLP) to explore Peierls stress and dislocation dynamics in zinc sulfide (ZnS) under both ground and excited states. Our results reveal that photoexcitation significantly increases Peierls stress by reducing strain concentration at the dislocation core, contributing to the transition from ductility to brittleness under light exposure. Importantly, this enhancement occurs without substantial changes in the dislocation core structure. These insights provide an understanding of the atomic-scale mechanisms behind photoplasticity in ZnS, demonstrating that integrating CDFT with MLP is a highly accurate and efficient approach to study complex material behaviors under photoexcitation.
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- Award ID(s):
- 2347218
- PAR ID:
- 10614950
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- ACS Materials Letters
- Volume:
- 7
- Issue:
- 1
- ISSN:
- 2639-4979
- Page Range / eLocation ID:
- 46 to 51
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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