Molecular dynamics simulations are used to investigate the mechanical properties of finite-width nanocrystalline gold nanoribbons with a thickness of one grain size under tensile strain. We find strong variations in the Young's modulus and flow stress especially for the sample with narrow width. With statistical analysis, Young's modulus has a trend of increase with the decrease of width. Flow stress does not follow this trend. Ductile fracture is observed at large strain in these nanocrystalline nanoribbons, but the fracture strain and mechanism are different from those of thick films as observed in existing experiments. For small widths below 80 nm, fracture is a necking effect, while for larger widths, shear bands and formation of nanovoids due to stress concentration are the main mechanism. Voids are mainly distributed in special GBs that are parallel to the direction of the maximum principal stress of the plastic deformation tensor. We find there is a width regime (about 80–130 nm) for the ultrathin nanoribbon gold, which have good ductility and large fracture strain.

中文翻译：

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纳米金超薄纳米带的变形和韧性断裂：宽度效应

分子动力学模拟用于研究在拉伸应变下厚度为一种晶粒尺寸的有限宽度纳米晶金纳米带的机械性能。我们发现杨氏模量和流动应力的变化很大，特别是对于窄宽度的样品。经统计分析，杨氏模量有随宽度减小而增大的趋势。流动应力不遵循这一趋势。在这些纳米晶纳米带中观察到大应变下的韧性断裂，但断裂应变和机制与现有实验中观察到的厚膜不同。对于小于 80 nm 的小宽度，断裂是颈缩效应，而对于较大的宽度，剪切带和由于应力集中导致的纳米空隙的形成是主要机制。空隙主要分布在平行于塑性变形张量最大主应力方向的特殊GB中。我们发现超薄纳米带金有一个宽度范围（约 80-130 nm），具有良好的延展性和大的断裂应变。