Structure of jammed ellipse packings with a wide range of aspect ratios
Structure of jammed ellipse packings with a wide range of aspect ratios
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各种长径比卡紧椭圆填料的结构
DOI：
10.1039/d3sm00705g
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发表时间：
2023
期刊：
影响因子：
3.4
通讯作者：
Hoy, Robert S.
中科院分区：
文献类型：
--
作者：
Rocks, Sebastian;Hoy, Robert S.
部分受到最近对椭圆体胶体悬浮液中液体玻璃的观察的启发，我们在比以前尝试过的更广泛的颗粒长宽比（α，长轴和短轴长度之比）范围内检查了堵塞的二维椭圆填料的结构。我们高精度地确定了干扰密度 phiJ(α)，并找到了经验分析公式，对于所有 1≤α≤10、三种不同的粒子分散度，将 phiJ(α) 预测在小于 0.1% 的范围内。然后我们探讨这些填料的局部结构顺序如何随 α 变化。我们发现最致密的堆积具有异常明确的最近邻壳层，包括具有恰好六个接触点的较高分数 fZ=6 的粒子和之前未报告的短程有序，其位置-方向对相关函数 g(r,Δθ) 中以“动力学抑制”区域为标志。我们还表明，随着 α 的增加，先前报道的等静压方法（配位数 ZJ → Ziso == 6）会被中断，然后随着局部向列序的增加而反转：ZJ(α) 下降到 4，因为椭圆更经常被两侧平行取向的邻居和两端垂直取向的邻居的接触所捕获。最后，我们表明，对于在压缩过程中不会产生大量局部六方或向列序的系统，φJ/φs（其中 φs 是饱和 RSA 堆积密度）几乎与 α 无关。
Motivated in part by the recent observation of liquid glass in suspensions of ellipsoidal colloids, we examine the structure of jammed two-dimensional ellipse packings over a much wider range of particle aspect ratios (α, the ratio of the major and minor axis lengths) than has been previously attempted. We determine the jamming densities ϕJ(α) to high precision, and find empirical analytic formulae that predict ϕJ(α) to within less than 0.1% for all 1≤α≤10, for three different particle dispersities. Then we explore how these packings’ local structural order varies with α. We find that the densest packings possess unusually-well-defined nearest-neighbor shells, including both a higher fraction fZ=6 of particles with exactly six contacts and a previously-unreported short-range order marked by “kinetically suppressed” regions in their positional–orientational pair correlation function g(r,Δθ). We also show that the previously-reported approach to isostaticity (coordination number ZJ → Ziso ≡ 6) with increasing α is interrupted and then reversed as local nematic order increases: ZJ(α) drops towards 4 as ellipses are more often trapped by contacts with a parallel-oriented neighbor on either side and a perpendicularly-oriented neighbor on either end. Finally we show that ϕJ/ϕs (where ϕs is the saturated RSA packing density) is nearly α-independent for systems that do not develop substantial local hexatic or nematic order during compression.