Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India.
Soft Matter. 2019 Oct 30;15(42):8483-8495. doi: 10.1039/c9sm00998a.
We present a numerical study of the phase behavior of repulsively interacting active polar particles that align their active velocities nematically. The amplitude of the active velocity, and the noise in its orientational alignment control the active nature of the system. At high values of orientational noise, the structural fluid undergoes a continuous nematic-isotropic transition in active orientation. This transition is well separated from an active phase separation, characterized by the formation of high density hexatic clusters, observed at lower noise strengths. With increasing activity, the system undergoes a re-entrant fluid - phase separation - fluid transition. The phase coexistence at low activity can be understood in terms of motility induced phase separation. In contrast, the re-melting of hexatic clusters, and the collective motion at low orientational noise are dominated by flocking behavior. At high activity, sliding and jamming of polar sub-clusters, formation of grain boundaries, lane formation, and subsequent fragmentation of the polar patches mediate remelting.
我们呈现了一个数值研究，研究了相互排斥的活跃极性粒子的相行为，这些粒子在向列排列中对齐它们的活跃速度。活跃速度的幅度和其方向对准的噪声控制着系统的活跃性质。在高取向噪声值下，结构流体在活跃取向中经历连续的向列-各向同性转变。这种转变与由高密度六方晶团簇形成的活跃相分离很好地区分开来，这种活跃相分离发生在较低的噪声强度下。随着活性的增加，系统经历了再进入的流体-相分离-流体转变。在低活性下的相共存可以用运动诱导相分离来理解。相比之下，在低取向噪声下，六方晶团簇的再熔化和集体运动主要由 flock 行为主导。在高活性下，极性亚团簇的滑动和堵塞、晶界的形成、车道的形成以及随后的极性斑块的碎裂介导了再熔化。
