Λ -Invariant and Topological Pathways to Influence the Strength of Submicron Crystals
Λ -Invariant and Topological Pathways to Influence the Strength of Submicron Crystals
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Î -影响亚微米晶体强度的不变和拓扑途径
DOI：
10.1103/physrevlett.124.205502
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发表时间：
2020
影响因子：
8.6
通讯作者：
Po, Giacomo
中科院分区：
文献类型：
--
作者：
Papanikolaou, Stefanos;Po, Giacomo
在小体积中，已知样品尺寸强烈影响机械行为：特别是强度和晶体塑性。这种相关性在所谓的“中尺度”上逐渐消失，在实验和模拟中，中尺度的定义都是几微米。然而，这幅图依赖于初始缺陷配置的“纠缠”。在这封信中，我们通过使用一种新的可观察到的位错集成（不变量）来研究位错拓扑的影响，它只依赖于相互的位错连接：它建立在位错的自然涡旋特征上，并且它具有连续离散的对应关系，可以帮助多尺度建模描述。我们利用有限体积的三维离散位错动力学模拟研究了亚微米级柱中任意复杂的初始位错微观结构。我们演示了如何通过偏随机位错环沉积或连续的压缩和扭转机械载荷来设计与样品尺寸无关的纳米级位错集成。
In small volumes, sample dimensions are known to strongly influence mechanical behavior: especially strength and crystal plasticity. This correlation fades away at the so-called “mesoscale,” loosely defined at several micrometers in both experiments and simulations. However, this picture depends on the “entanglement” of the initial defect configuration. In this Letter, we study the effect of dislocation topology through the use of a novel observable for dislocation ensembles (theinvariant) that depends only on mutual dislocation linking: It is built on the natural vortex character of dislocations, and it has a continuum-discrete correspondence that may assist multiscale modeling descriptions. We investigate arbitrarily complex initial dislocation microstructures in sub-micron-sized pillars using three-dimensional discrete dislocation dynamics simulations for finite volumes. We demonstrate how to engineer nanoscale dislocation ensembles that are independent from sample dimensions, either by biased-random dislocation loop deposition or by sequential mechanical loads of compression and torsion.