Jamming in Model Supercooled Liquids and Athermal Systems

模型过冷液体和无热系统中的干扰

• 批准号: 0087349
• 负责人: Andrea Liu
• 金额: $ 24.6万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-11-01 至 2004-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0087349&HistoricalAwards=false
• 关键词: Jamming; Model; Supercooled; Liquids; Athermal

0087349LiuThis grant supports theoretical and computational research on the properties of disordered systems. In particular, research will be done on the concept of jamming. Many systems with no quenched disorder can jam, i.e., develop a yield stress or an immeasurably long stress relaxation time in a disordered state. These systems include supercooled liquids, colloidal suspensions, granular materials, emulsions and foams. It has recently been suggested that the onset of jamming might lead to some degree of universality. This is the concept of jamming. Specifically, it has been suggested that different systems should show similar behavior as they jam, and that each system has a jamming phase diagram.The concept of jamming will be explored using numerical simulations on two very different systems that both exhibit transitions to constrained dynamics. The first is a quiescent thermal system, namely a binary Lennard-Jones mixture. This model has been shown to jam as the temperature is lowered to the glass transition. The second system to be studied is a driven, athermal system that has been shown to jam as the shear stress is lowered to the yield stress or as the density of particles is raised above close-packing.One objective of the proposed research is to exploit the idea of jamming to gain new insight into the glass transition by applying recent ideas from granular materials (namely force chains) to supercooled liquids. We will also test the idea of jamming by calculating the complete jamming phase diagram for a binary Lennard-Jones mixture. Finally, we will test whether shear-induced fluctuations can be described by an enhanced effective temperature in binary Lennard-Jones mixtures. The idea of an effective temperature is already widely used to describe unjammed granular materials and needs to be examined carefully.At a minimum, we will learn much more about the behavior of two intriguing systems (supercooled liquids and sheared athermal packings), even if we discover that their connection is only superficial. If the concept of jamming is correct, however, it will be extremely powerful because ideas derived from one system will be applicable to another. The recognition that different systems can be viewed within a broader framework has revolutionalized a number of fields in the past. It is important to explore the avenue of jamming because it may lead to new and deeper understanding of long unsolved problems such as the glass transition.%%% This grant supports theoretical and computational research on the properties of disordered systems. In particular, research will be done on the concept of jamming. Jamming commonly occurs to most of us in the form of traffic jams. As too many vehicles try to pass through a constrained path, the smooth flow of traffic becomes stopped or jammed. Many physical systems comprised of many particles can also jam, i.e., develop a yield stress or an immeasurably long stress relaxation time in a disordered state. These systems include supercooled liquids, colloidal suspensions, granular materials, emulsions and foams. It has recently been suggested that the onset of jamming might lead to some degree of universality among these diverse systems. This is the concept of jamming. Specifically, it has been suggested that different systems should show similar behavior as they jam, and that each system has a jamming phase diagram. In this research the concept of jamming will be explored using numerical simulations on two very different systems that both exhibit transitions to constrained dynamics. ***

0087349Liu这项资助支持对无序系统特性的理论和计算研究。 特别是，将研究干扰的概念。 许多没有淬火无序的系统可能会堵塞，即在无序状态下产生屈服应力或不可估量的长应力松弛时间。 这些系统包括过冷液体、胶体悬浮液、颗粒材料、乳液和泡沫。 最近有人提出，干扰的出现可能会导致某种程度的普遍性。 这就是干扰的概念。 具体来说，有人建议不同的系统在干扰时应该表现出相似的行为，并且每个系统都有一个干扰相图。干扰的概念将通过对两个非常不同的系统进行数值模拟来探索，这两个系统都表现出向约束动态的过渡。 第一个是静态热系统，即二元伦纳德-琼斯混合物。 当温度降至玻璃化转变温度时，该模型已被证明会堵塞。 要研究的第二个系统是一个驱动的无热系统，当剪切应力降低到屈服应力或颗粒密度提高到密堆积以上时，该系统会发生堵塞。本研究的一个目标是利用通过应用从颗粒材料（即力链）到过冷液体的最新想法，干扰的想法获得了对玻璃化转变的新见解。 我们还将通过计算二元 Lennard-Jones 混合物的完整干扰相图来测试干扰的想法。 最后，我们将测试是否可以通过二元 Lennard-Jones 混合物中增强的有效温度来描述剪切引起的波动。 有效温度的概念已经广泛用于描述未堵塞的颗粒材料，需要仔细检查。至少，我们将更多地了解两个有趣的系统（过冷液体和剪切非热填料）的行为，即使我们发现他们的联系只是表面的。 然而，如果干扰的概念是正确的，它将非常强大，因为源自一个系统的想法将适用于另一个系统。 人们认识到可以在更广泛的框架内看待不同的系统，这在过去已经彻底改变了许多领域。 探索干扰途径非常重要，因为它可能会带来对玻璃化转变等长期未解决的问题的新的、更深入的理解。%%% 这项资助支持对无序系统特性的理论和计算研究。 特别是，将研究干扰的概念。 对于我们大多数人来说，堵塞通常以交通堵塞的形式发生。 由于太多车辆试图通过受限制的道路，顺畅的交通就会停止或堵塞。 许多由许多颗粒组成的物理系统也会堵塞，即在无序状态下产生屈服应力或不可估量的长应力松弛时间。 这些系统包括过冷液体、胶体悬浮液、颗粒材料、乳液和泡沫。 最近有人提出，干扰的出现可能会导致这些不同系统之间出现某种程度的普遍性。 这就是干扰的概念。具体来说，有人建议不同的系统在干扰时应表现出相似的行为，并且每个系统都有一个干扰阶段图。 在这项研究中，将通过对两个截然不同的系统进行数值模拟来探索干扰的概念，这两个系统都表现出向约束动力学的转变。 ***