Liao Guo-Jun, Hall Carol K, Klapp Sabine H L
Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany.
Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
Soft Matter. 2020 Mar 4;16(9):2208-2223. doi: 10.1039/c9sm01539f.
Based on Brownian Dynamics (BD) simulations, we study the dynamical self-assembly of active Brownian particles with dipole-dipole interactions, stemming from a permanent point dipole at the particle center. The propulsion direction of each particle is chosen to be parallel to its dipole moment. We explore a wide range of motilities and dipolar coupling strengths and characterize the corresponding behavior based on several order parameters. At low densities and low motilities, the most important structural phenomenon is the aggregation of the dipolar particles into chains. Upon increasing the particle motility, these chain-like structures break, and the system transforms into a weakly correlated isotropic fluid. At high densities, we observe that the motility-induced phase separation is strongly suppressed by the dipolar coupling. Once the dipolar coupling dominates the thermal energy, the phase separation disappears, and the system rather displays a flocking state, where particles form giant clusters and move collective along one direction. We provide arguments for the emergence of the flocking behavior, which is absent in the passive dipolar system.
基于布朗动力学（BD）模拟，我们研究了具有偶极 - 偶极相互作用的活性布朗粒子的动力学自组装，这种相互作用源于粒子中心的永久点偶极。每个粒子的推进方向被选择为与其偶极矩平行。我们探索了广泛的迁移率和偶极耦合强度，并基于几个序参量来表征相应的行为。在低密度和低迁移率下，最重要的结构现象是偶极粒子聚集成链。随着粒子迁移率的增加，这些链状结构会断裂，系统转变为弱相关的各向同性流体。在高密度下，我们观察到迁移率诱导的相分离受到偶极耦合的强烈抑制。一旦偶极耦合主导热能，相分离就会消失，系统反而呈现出聚集状态，即粒子形成巨大的团簇并沿一个方向集体移动。我们为聚集行为的出现提供了论据，而这种行为在被动偶极系统中是不存在的。
