Agrawal Naveen Kumar, Mahapatra Pallab Sinha
Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, India.
Phys Rev E. 2020 Apr;101(4-1):042607. doi: 10.1103/PhysRevE.101.042607.
We study phase transition in a binary system of monodisperse active and passive particles. The particles are initially randomly positioned inside a fixed boundary square enclosure. The active particles can move with their self-propulsion force. Whereas, the passive particles do not have any self-propulsion force, and they move by the spatial interactions with other particles. An alignment force in our discrete element model causes the emergence of collective milling motion. Without this alignment interaction, the particle system remains in a disordered phase. Whereas, the ordered milling phase is attained after achieving a minimum coordination among neighboring particles. The phase transition from disordered to ordered depends upon the relative effect of self-propulsion and the alignment, initial states of the particles, noise level, and the fraction of the active particles present in the system. The phase transition we observed is of first-order nature.
我们研究单分散活性粒子和被动粒子二元系统中的相变。粒子最初随机分布在固定边界的方形封闭空间内。活性粒子可以凭借自身推进力移动。而被动粒子没有任何自身推进力，它们通过与其他粒子的空间相互作用而移动。我们离散元模型中的排列力导致了集体研磨运动的出现。没有这种排列相互作用，粒子系统将保持在无序相。而在相邻粒子之间达到最小协调性后，就会进入有序研磨相。从无序到有序的相变取决于自身推进力和排列的相对作用、粒子的初始状态、噪声水平以及系统中活性粒子的比例。我们观察到的相变是一阶性质的。
