Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
J Chem Phys. 2022 Dec 14;157(22):224902. doi: 10.1063/5.0127569.
Recent years have seen a rapid increase of interest in dense active materials, which, in the disordered state, share striking similarities with the conventional passive glass-forming matter. For such passive glassy materials, it is well established (at least in three dimensions) that the details of the microscopic dynamics, e.g., Newtonian or Brownian, do not influence the long-time glassy behavior. Here, we investigate whether this still holds true in the non-equilibrium active case by considering two simple and widely used active particle models, i.e., active Ornstein-Uhlenbeck particles (AOUPs) and active Brownian particles (ABPs). In particular, we seek to gain more insight into the role of the self-propulsion mechanism on the glassy dynamics by deriving a mode-coupling theory (MCT) for thermal AOUPs, which can be directly compared to a recently developed MCT for ABPs. Both theories explicitly take into account the active degrees of freedom. We solve the AOUP- and ABP-MCT equations in two dimensions and demonstrate that both models give almost identical results for the intermediate scattering function over a large variety of control parameters (packing fractions, active speeds, and persistence times). We also confirm this theoretical equivalence between the different self-propulsion mechanisms numerically via simulations of a polydisperse mixture of active quasi-hard spheres, thereby establishing that, at least for these model systems, the microscopic details of self-propulsion do not alter the active glassy behavior.
近年来,人们对密集活性物质的兴趣迅速增加,这些物质在无序状态下与传统的被动玻璃形成物质具有惊人的相似之处。对于这种被动玻璃状材料,已经确立(至少在三维空间中)微观动力学的细节,例如牛顿或布朗,不会影响长时间的玻璃态行为。在这里,我们通过考虑两种简单而广泛使用的活性粒子模型,即活性奥恩斯坦 - 乌伦贝克粒子(AOUP)和活性布朗粒子(ABP),来研究这种情况在非平衡活性情况下是否仍然成立。特别是,我们通过为热 AOUP 推导出模式耦合理论(MCT),寻求更深入地了解自推进机制对玻璃态动力学的作用,该理论可以与最近开发的 ABP 的 MCT 直接比较。这两个理论都明确地考虑了活性自由度。我们在二维空间中求解了 AOUP 和 ABP-MCT 方程,并证明了这两个模型在各种控制参数(堆积分数、活性速度和持续时间)下对中间散射函数给出了几乎相同的结果。我们还通过对活性准硬球的多分散混合物的模拟,数值上证实了不同自推进机制之间的这种理论等价性,从而确立了,至少对于这些模型系统,自推进的微观细节不会改变活性玻璃态行为。