磁性和非磁性胶体中的玻璃态行为与动态阻滞
Glassiness and dynamic arrest in magnetic and non-magnetic colloids
- Indian Institute of Technology（印度理工学院）
- Chemnitz University of Technology（开姆尼茨工业大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过分子动力学模拟比较磁性和非磁性胶体，发现磁性流体的van Hove函数尾部更重，揭示了链状结构导致的动态异质性，增进了对磁响应胶体弛豫机制的理解。
AI中文摘要：
我们研究并比较了低温下单分散磁性和非磁性软球流体中一系列玻璃态指标，旨在探讨磁矩的影响。我们使用Stockmayer模型对磁性流体进行分子动力学模拟，并使用纯Lennard-Jones相互作用模拟非磁性情况。我们的研究涉及淬火实验，即两种系统被快速冷却至其冻结温度以下深处。尽管Lennard-Jones流体形成致密聚集体，但偶极相互作用的加入促进了分支状和开放形态的发展。在表征了冻结结构的静态性质后，我们重点关注其动力学。一个关键可观测量是van Hove函数的自部分，它测量粒子在时间t内位移距离Δ的概率。在两种流体中，该函数均表现出非高斯行为——这提供了动态异质性和玻璃态的特征。这种行为源于两个不同过程之间的时间尺度分离：逃逸其环境的移动粒子和在笼中振动的固定粒子。特别是，我们发现Stockmayer流体的van Hove函数具有更重的尾部，这是其中链状结构中强相关运动的结果。这些发现揭示了磁性流体中的核心弛豫机制，增进了我们对磁响应胶体系统的理解。
英文摘要：
We investigate and compare a range of indicators for glassiness in monodisperse magnetic and non-magnetic soft-sphere fluids at low temperatures with a view to exploring the effect of the magnetic moment. We perform extensive molecular dynamics simulations using the Stockmayer model for magnetic fluids and a pure Lennard-Jones interaction for the non-magnetic case. Our investigations involve quenching experiments, in which both systems are rapidly cooled deep below their freezing temperatures. Although the Lennard-Jones fluid forms compact aggregates, the inclusion of dipolar interactions promotes the development of branched and open morphologies. After characterizing the static properties of the frozen structures, we focus on their dynamics. A key observable is the self-part of the van Hove function, which measures the probability that a particle is displaced by a distance $Δ$ over time $t$. In both fluids, this function exhibits non-Gaussian behavior --- thereby providing a signature of dynamic heterogeneity and glassiness. This behavior stems from a separation of time scales between two distinct processes: mobile particles that escape their environments and immobile particles that vibrate within cages. In particular, we find a heavier tail in the van Hove function for the Stockmayer fluid, which is a consequence of the strongly correlated motion in chain-like structures found there. These findings shed light on core relaxation mechanisms in magnetic fluids, advancing our understanding of magnetically responsive colloidal systems.
