| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 101 === In many nanomaterials, metallic nanowires play an important role in many device components because of their excellent mechanical and electronic properties, which strongly depends on their nanoscale structures and high specific surface area that is very different from macroscale materials. On the other hand, twins are common defects in FCC materials, especially for Σ3 coherent twin boundary (CTB). Therefore, the twinned nanowires are widely discussed.
In this study, molecular dynamics simulation (MD simulation) was used to investigate the strength of twinned copper nanowires with various sizes and cross-sections. For cylindrical nanowires with [111]-orientation, the distribution of atomic stress (or potential energy) would be changed due to the introduction of Σ3 coherent twin boundaries perpendicular to the axial direction, which depended on the spacing of twins, and it could also change the strength of twinned nanowires with respect to the single crystal nanowires. Critical softening-hardening twin boundary spacing with respect to single crystal nanowires existed in twinned nanowires, which depended on the size of nanowires. Whether the stress (or potential energy) of atoms at surface could be redistributed effectively by twin boundaries or not determined the strength of twinned nanowires.
If considering the effect of cross-sections on twinned nanowires, the change of atomic configuration at surface due to introduction of twins was an important factor that could influence the strength of nanowires.
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