Strain rate-dependent tensile response of glassy silicon nanowires studied by accelerated atomistic simulations
Strain rate-dependent tensile response of glassy silicon nanowires studied by accelerated atomistic simulations
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DOI：
10.1063/5.0060136
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发表时间：
2021-08
影响因子：
3.2
通讯作者：
Yanming Zhang;P. Cao;Binghui Deng;Liping Huang;Yunfeng Shi
中科院分区：
文献类型：
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作者：
Yanming Zhang;P. Cao;Binghui Deng;Liping Huang;Yunfeng Shi
近年来，人们通过纳米力学实验和原子水平模拟对玻璃纳米线的力学性能进行了深入研究。遗憾的是，纳米力学测试的应变速率在实验和模拟之间存在着巨大的差距，这使得即使对于相同的材料体系，也难以对结果进行比较。本文采用基于自学习metabasin逃逸算法的加速原子模拟，研究了具有不同本构延展性的非晶Stillinger-Weber硅纳米线在1010 ~ 10−1 s−1应变速率下的拉伸力学性能。研究发现，随着应变速率的减小，脆性和延性玻璃硅纳米线的强度都有所减弱，这与协同剪切模型一致。此外，随着应变速率的减小，脆性纳米线的塑性量保持不变，而延性纳米线的塑性量则减小。这种塑性恶化是由于在低应变速率下应变局部化增强引起的。最后，我们表明，通过非仿射位移的距离矩阵，一个更分层的势能景观是导致韧性硅玻璃纳米线更高应变局部化倾向的原因。
Mechanical properties of glassy nanowires have been intensively investigated recently by both nanomechanical experiments and atomic-level simulations. Unfortunately, there exists a huge gap in the strain rate of the nanomechanical tests between experiments and simulations, which makes it difficult to compare results even for the same material system. Using accelerated atomistic simulations based on a self-learning metabasin escape algorithm, here, we report the tensile mechanical properties of amorphous Stillinger–Weber silicon nanowires with different intrinsic ductility under strain rates ranging from 1010 to 10−1 s−1. It is found that both brittle and ductile glassy silicon nanowires display weakened strength with a decreasing strain rate, in agreement with the cooperative shear model. Moreover, as the strain rate decreases, the amount of plasticity remains unchanged for the brittle nanowires, yet it decreases for the ductile ones. Such deteriorated plasticity in ductile glassy nanowires is caused by enhanced strain localization at low strain rates. Lastly, we show that via the distance matrix of nonaffine displacement, a more hierarchical potential energy landscape is responsible for the higher strain localization propensity in ductile silicon glassy nanowires.