Plastic flow in metallic glasses (MGs) is known to be mediated by shear transformations (STs), which have been hypothesized to preferentially initiate from identifiable local “defect” regions with loose atomic packing. Here we show that the above idea is incorrect, i.e., STs do not arise from signature structural defects that can be recognized a priori . This conclusion is reached via a realistic MG model obtained by combining molecular dynamics (MD) and Monte Carlo simulations, achieving liquid solidification at an effective cooling rate as slow as 500 K/s to approach that typical in experiments for producing bulk MGs. At shear stresses before global yielding, only about 2% of the total atoms participate in STs, each event involving typically ~10 atoms. These observations rectify the excessive content of “liquid-like regions” retained from unrealistically fast quench in MD-produced glass models. Our findings also shed light on the indeterministic aspect of the ST sites/zones, which emerge with varying spatial locations and distribution depending on specific mechanical loading conditions.

中文翻译：

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金属玻璃的剪切变换没有过多和可预定义的缺陷

已知金属玻璃 (MG) 中的塑性流动是由剪切变换 (ST) 介导的，据推测，剪切变换优先从具有松散原子堆积的可识别局部“缺陷”区域开始。这里我们证明上述想法是不正确的，即ST不是由可以识别的签名结构缺陷引起的先验. 该结论是通过结合分子动力学 (MD) 和蒙特卡洛模拟获得的真实 MG 模型得出的，该模型以低至 500 K/s 的有效冷却速率实现液体凝固，接近生产块状 MG 的典型实验。在全局屈服之前的剪切应力下，只有大约 2% 的原子参与 ST，每个事件通常涉及约 10 个原子。这些观察结果纠正了 MD 生产的玻璃模型中因不切实际的快速淬火而保留的“类液体区域”的过量含量。我们的研究结果还揭示了 ST 站点/区域的不确定性方面，这些站点/区域根据特定的机械负载条件出现不同的空间位置和分布。