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. ***

0087349 Liu该基金支持对无序系统性质的理论和计算研究。 特别是，将对干扰的概念进行研究。 许多没有淬灭无序的系统可能堵塞，即，在无序状态下产生屈服应力或不可测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，干扰的开始可能导致某种程度的普遍性。 这就是干扰的概念。 具体来说，它已被建议，不同的系统应该表现出类似的行为，因为他们的干扰，每个系统都有一个干扰phase diagrams.干扰的概念将探讨使用两个非常不同的系统，都表现出过渡到约束动力学的数值模拟。 第一种是静态热系统，即二元Lennard-Jones混合物。 随着温度降低到玻璃化转变，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，非热系统，已被证明堵塞的剪切应力降低到屈服应力或颗粒的密度提高以上密堆积的建议research.One的目标是利用堵塞的想法，获得新的洞察到玻璃化转变的应用最近的想法从粒状材料（即力链）的过冷液体。 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，我们将测试是否剪切引起的波动可以描述一个增强的有效温度在二元Lennard-Jones混合物。 有效温度的概念已经被广泛用于描述未堵塞的颗粒物质，需要仔细研究。至少，我们将更多地了解两个有趣系统（过冷液体和剪切无热填料）的行为，即使我们发现它们之间的联系只是表面的。 然而，如果干扰的概念是正确的，它将是极其强大的，因为来自一个系统的思想将适用于另一个系统。 认识到可以在更广泛的框架内看待不同的系统，在过去已经彻底改变了许多领域。 探索干扰的途径很重要，因为它可能会导致对长期未解决的问题（如玻璃化转变）的新的和更深入的理解。该补助金支持对无序系统性质的理论和计算研究。 特别是，将研究干扰的概念。 我们大多数人经常遇到交通堵塞的情况。 当太多的车辆试图通过一条受限的路径时，顺畅的交通流就会停止或堵塞。 由许多粒子组成的许多物理系统也可能堵塞，即，在无序状态下产生屈服应力或不可测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，干扰的开始可能导致这些不同系统之间某种程度的普遍性。 这就是干扰的概念。具体来说，有人建议，不同的系统应该表现出类似的行为，因为他们堵塞，每个系统都有一个干扰相图。 在这项研究中，干扰的概念将探讨使用两个非常不同的系统，都表现出过渡到约束动力学的数值模拟。***