Dynamically crowded solutions of infinitely thin Brownian needles.
Dynamically crowded solutions of infinitely thin Brownian needles.
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DOI：
10.1103/physreve.96.012118
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
Sebastian Leitmann;F. Höfling;T. Franosch
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文献类型：
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作者：
Sebastian Leitmann;F. Höfling;T. Franosch
我们研究的解决方案的无限薄针密度深的半稀制度的布朗动力学模拟。对于高密度，这些解决方案变得强烈纠缠和针的运动基本上是限制在一个一维的限制管相邻的针组成的滑动。从取向和平移扩散的密度依赖行为，我们提取的长时间输运系数和约束管的几何形状。管内的滑动运动在平移运动的非高斯参数中变得可见，在中间时间作为扩展的平台，并且在中间散射函数中作为代数衰减。这种瞬态动态逮捕也证实了垂直于针轴的均方位移的局部指数。此外，垂直于针的位移的概率分布变得强烈非高斯;相反，对于大位移，它显示指数分布。另一方面，基于对取向高阶关联的分析，我们发现，强约束下的旋转运动又变成了扩散运动。在粗粒度的时间和长度尺度上，高纠缠的针的时空动力学被捕获的一个自由扩散的幻影针与长时间的输运系数从针在溶液中获得。与时间相关的动力学的幻影针也进行了评估分析方面的球状波函数。针在溶液中的动态行为被发现是相同的针洛伦兹系统，其中示踪针探索淬火无序阵列的其他针。
We study the dynamics of solutions of infinitely thin needles up to densities deep in the semidilute regime by Brownian dynamics simulations. For high densities, these solutions become strongly entangled and the motion of a needle is essentially restricted to a one-dimensional sliding in a confining tube composed of neighboring needles. From the density-dependent behavior of the orientational and translational diffusion, we extract the long-time transport coefficients and the geometry of the confining tube. The sliding motion within the tube becomes visible in the non-Gaussian parameter of the translational motion as an extended plateau at intermediate times and in the intermediate scattering function as an algebraic decay. This transient dynamic arrest is also corroborated by the local exponent of the mean-square displacements perpendicular to the needle axis. Moreover, the probability distribution of the displacements perpendicular to the needle becomes strongly non-Gaussian; rather, it displays an exponential distribution for large displacements. On the other hand, based on the analysis of higher-order correlations of the orientation we find that the rotational motion becomes diffusive again for strong confinement. At coarse-grained time and length scales, the spatiotemporal dynamics of the needle for the high entanglement is captured by a single freely diffusing phantom needle with long-time transport coefficients obtained from the needle in solution. The time-dependent dynamics of the phantom needle is also assessed analytically in terms of spheroidal wave functions. The dynamic behavior of the needle in solution is found to be identical to needle Lorentz systems, where a tracer needle explores a quenched disordered array of other needles.