Hierarchical glass transition of hard hemidisks with local assemblies.,Soft Matter

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Hierarchical glass transition of hard hemidisks with local assemblies.
Soft Matter ( IF 2.9 ) Pub Date : 2020-09-03 , DOI: 10.1039/d0sm01003k
Wei Zheng ₁ , Qun-Li Lei ₂ , Yuqiang Ma ₃ , Ran Ni ₂

Affiliation

Using computer simulation, we investigate the glass transition of a two-dimensional hard-hemidisk system. Upon increasing the packing fraction of the system, we find that the system vitrifies into a glass with local assembled discal “dimers”, which are free to rotate in a collective way. The rotational mean square displacement does not exhibit the typical plateau (slowdown) like what occurs in the translational mean square displacement. This effect induces a pronounced violation of the rotational Stokes–Einstein relationship compared with the translational degree of freedom at the supercooled region. However, the obtained glass transition points in these two freedom degrees are found to be the same within the numerical accuracy, which is due to the strong positive spatial and dynamic correlation between translational and rotational slow-moving particles. Moreover, we find that the locally assembled dimers can serve as fast rotating gears facilitating the orientational relaxation in the system, and this suggests that the locally favored finite structures play an important role in the hierarchical glass transition of anisotropic colloids.

中文翻译：

具有本地程序集的硬半磁盘的分层玻璃过渡。

使用计算机仿真，我们研究了二维硬磁盘系统的玻璃化转变。随着系统填充率的增加，我们发现该系统玻璃化为带有局部组装的圆盘“二聚体”的玻璃，该二聚体可以自由地集体旋转。旋转均方位移不像平移均方位移那样表现出典型的平稳期（减速）。与过冷区域的平移自由度相比，该效应明显违反了旋转斯托克斯-爱因斯坦关系。但是，发现在这两个自由度中获得的玻璃化转变点在数值精度内是相同的，这是由于平移和旋转缓慢移动的粒子之间存在强烈的正空间和动态相关性。此外，我们发现局部组装的二聚体可以用作促进系统中取向松弛的快速旋转齿轮，这表明局部偏爱的有限结构在各向异性胶体的分级玻璃化转变中起重要作用。

更新日期：2020-09-16

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