Monodisperse suspensions of Brownian colloidal spheres crystallize at high densities, and ordering under shear has been observed at densities below the crystallization threshold. We perform large-scale simulations of a model suspension containing over ${10}^5$ particles to quantitatively study the ordering under shear and to investigate its link to the rheological properties of the suspension. We find that at high rates, for $Pe>1$, the shear flow induces an ordering transition that significantly decreases the measured viscosity. This ordering is analyzed in terms of the development of layering and planar order, and we determine that particles are packed into hexagonal crystal layers (with numerous defects) that slide past each other. By computing local ${\psi }_6$ and ${\psi }_4$ order parameters, we determine that the defects correspond to chains of particles in a squarelike lattice. We compute the individual particle contributions to the stress tensor and discover that the largest contributors to the shear stress are primarily located in these lower density, defect regions. The defect structure enables the formation of compressed chains of particles to resist the shear, but these chains are transient and short-lived. The inclusion of a contact friction force allows the stress-bearing structures to grow into a system-spanning network, thereby disrupting the order and drastically increasing the suspension viscosity.

中文翻译：

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剪切致密悬浮液中的有序域：与粘度和摩擦破坏效应的联系

布朗胶体球的单分散悬浮液在高密度下结晶，在低于结晶阈值的密度下观察到剪切下的有序性。我们对包含超过${10}^5$颗粒定量研究剪切下的排序并研究其与悬浮液流变特性的联系。我们发现，在高利率下，对于$磷e>1$，剪切流引起有序转变，显着降低了测量的粘度。根据分层和平面顺序的发展来分析这种排序，我们确定粒子被填充到相互滑过的六方晶体层（具有许多缺陷）中。通过计算本地${\psi }_6$和${\psi }_4$序参数，我们确定缺陷对应于方形晶格中的粒子链。我们计算了单个粒子对应力张量的贡献，并发现剪切应力的最大贡献者主要位于这些密度较低的缺陷区域。缺陷结构能够形成压缩的颗粒链来抵抗剪切，但这些链是短暂的和短暂的。包含接触摩擦力允许应力承载结构成长为系统跨越网络，从而破坏秩序并显着增加悬浮液粘度。