活性玻璃形成体中协同重排区的形貌
Morphology of cooperatively rearranging regions in active glass formers
摘要：
随着温度向玻璃化转变（$T_{g}$）降低，过冷液体显示出越来越多的非均匀动力学。这种动力学异质性的一个标志是由快速移动的粒子组成的合作重排区（CRR）的自发出现。虽然已经非常详细地探索了被动玻璃形成器中的这些CRR，但是对主动玻璃形成器的理解受到严重限制。关于被动玻璃成形器中CRR的形态的现有共识优先考虑其快速子集，其由快速移动的颗粒组成。在本研究中，我们专注于合成的非热活性玻璃形成剂，并显示出同样的贡献，从慢子集的形态的CRR。这两个子集在其结构中表现出指数分布，这与CRR的存在密切相关。有趣的是，我们还观察到，这些子集的分形维数（$d_{\text{f}}$）共享字符串和紧凑的形态，往往以相反的方式变化的控制参数，即持续时间（$τ_{p}$）和有效温度（$T_{\text{eff}}$）。分形维数$d_{\text{f}}$测量分形对象在其边界处的粗糙度或简单地说是紧凑度。更准确地说，分子松散地结合在边界粗糙的结构中，因此这种条件有利于其在尺寸和形状方面的结构变化。这也是一个事实，任何结构变化是在玻璃形成液体的背景下的弛豫动力学的签名。因此，在本研究中，我们观察到$d_{\text{f}}$与$T_{\text{eff}}$和$τ_{p}$的变化，从形态变化的见解，导致结构变化，无论是在BD极限和非平衡极限。
英文摘要：
Super cooled liquids display increasingly heterogeneous dynamics as temperature is lowered towards the glass transition ($T_{g}$). A hallmark of this dynamical heterogeneity is the spontaneous emergence of cooperative rearranging regions (CRRs) composed of fast moving particles. While these CRRs in passive glass formers have been explored in great detail, thus understanding is severely limited in active glass formers. The existing consensus on the morphology of CRRs in a passive glass former prioritizes its fast subsets, composed of fast moving particles. In the present study, we focus on a synthetic athermal active glass former and show an equal contribution for the morphology of CRRs from slow subsets as well. Both these subsets exhibit an exponential distribution in their structure which strongly correlates with the existence of CRRs. Interestingly, we also observe that the fractal dimensions ($d_{\text{f}}$) of these subsets share both string and compact like morphology that tends to vary in opposite fashion with the control parameters, namely the persistent time ($τ_{p}$) and the effective temperature ($T_{\text{eff}}$). The fractal dimension $d_{\text{f}}$ measures the roughness or put simply the compactness of fractal objects at their boundaries. More precisely, molecules are loosely bound in a structure for which boundary is rough and thereby this condition facilitates its structural change in terms of size and shape. It is also a fact that any structural change is a signature of relaxation dynamics in the context of glass forming liquids. Thus, in the present study, we observe a change in $d_{\text{f}}$ with $T_{\text{eff}}$ and $τ_{p}$ from the insights of morphology variation that causes structural change, both in the BD limit and non-equilibrium limit.
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