Statics and Dynamics of Materials with Quenched Disorder

淬火无序材料的静力学和动力学

• 批准号: 0606424
• 负责人: A. Alan Middleton
• 金额: $ 27.9万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0606424&HistoricalAwards=false
• 关键词: Statics; Dynamics; Materials; Quenched; Disorder

This project is a theoretical exploration of material systems that are controlled by disorder. Disorder is prevalent in materials and is central to experiments ranging from electronic transport in porous conductors or nanoscopic dot arrays through the dynamics of colloidal systems and of domain walls in magnetic films. The principal investigator ( PI) will carry out extensive numerical simulations using models of (1) inhomogeneous magnets and interfaces with competing interactions and (2) the flow of particles in materials with random pinning. The PI will also pursue a better description the apparent connections between the algorithms used to study disordered materials and the theoretical pictures of the models. These strands link computer science methods and physical pictures, which share a fundamental mathematical basis in graph theory and statistical mechanics.Intellectual merit: The description of materials by coarse-grained models, which capture the essential energetics and dynamics using (mostly) classical degrees of freedom, has provided fundamental insight into the phases and dynamics of condensed matter. Simulations of such models provide both quantitative predictions and qualitative descriptions; they are especially needed for understanding the collective behavior of disordered materials, for which clear analytic answers are often lacking.The PI has studied and developed optimization algorithms to study the low temperature behavior of such models for disordered magnets, such as the random field Ising magnet and spin glasses, and will improve simulations to build more coherent pictures of disordered systems. The PI will also develop new schemes for computing barriers to relaxation and accelerating the dynamics of glassy systems, in order to study aging and memory effects over a wide range of time scales. Better understanding of algorithms for studying ground states and dynamics will be closely linked to physical pictures of these models.The study of transport in condensed matter systems encompasses many distinct problems, depending on whether quantum effects are important, the role of temperature, the strength of the interactions, etc. The PI will study the set of problems relevant to degrees of freedom that are best described at the mesoscopic scale, where quantum effects are negligible and the temperature is not large. Such problems include the transport of electrons between arrays of small particles, viscous fluids in porous media, and magnetic vortices in superconductors.An anisotropic coarse-grained model, developed by the PI and collaborators for studying plastic flow with conservation laws, will be studied in detail. In addition to investigating randomness in these systems, the PI will simulate the response of designed quasiperiodic systems to ac drives, such as might be realized with colloidal particles.Broader impact: Progress on the specific scientific goals of this project will be closely connected with more general benefits. The PI will train graduate students and postdoctoral researchers, with an important focus on the overlap between direct simulation, advanced algorithms, and condensed matter physics. The models to be studied are prototypes for disordered materials and have inspired physical pictures for a wide range of systems, including quantum critical points in the presence of disorder and the folding of biopolymers. Progress on understanding the statics and dynamics of disordered systems, including domain structure and hysteresis, has eventual application to materials development, including magnetic memories. This work will strengthen connections between ideas in computer science (algorithms for combinatorial optimization and their running time) and physics (lengths scales and dynamics infinite-dimensional materials). The computer programs developed by the PI will be made generally available. The PI is active in sharing science with the local community through presentations and activities related to condensed matter physics.Non-Technical Abstract: This theoretical project will explore materials and condensed systems whose properties are determined by disorder. Classic solid state materials are characterized by atoms arranged in perfect order. Yet most materials have some degree of disorder and some owe their unique properties to the presence of disorder. This research will use primarily numerical methods (computation) to study the effects of disorder on a variety of materials of current interest. The connection between the numerical methods used and the physical picture described can lead to advances in computer codes that have wider application. These connections will also be pursued.

这个项目是对由无序控制的材料系统的理论探索。无序在材料中很普遍，并且是实验的核心，从多孔导体中的电子输运或纳米级点阵列，到胶体系统的动力学和磁性薄膜中的畴壁。首席研究员（PI）将使用以下模型进行广泛的数值模拟：(1)具有竞争相互作用的非均匀磁体和界面；(2)具有随机钉钉的材料中的颗粒流动。PI还将更好地描述用于研究无序材料的算法与模型的理论图像之间的明显联系。这些线索将计算机科学方法和物理图像联系起来，它们在图论和统计力学中共享一个基本的数学基础。智力优势：用粗粒度模型描述材料，用（大部分）经典的自由度捕捉基本的能量学和动力学，为凝聚态物质的相和动力学提供了基本的见解。这些模型的模拟提供了定量预测和定性描述；它们对于理解无序材料的集体行为是特别需要的，对此通常缺乏明确的分析答案。PI研究并开发了优化算法，以研究无序磁体（如随机场伊辛磁体和自旋玻璃）的这种模型的低温行为，并将改进模拟，以构建更连贯的无序系统图像。为了在大范围的时间尺度上研究老化和记忆效应，PI还将开发新的方案来计算玻璃系统的弛豫障碍和加速动力学。更好地理解研究基态和动力学的算法将与这些模型的物理图像密切相关。凝聚态系统输运的研究包含许多不同的问题，这取决于量子效应是否重要、温度的作用、相互作用的强度等。PI将研究一系列与自由度相关的问题，这些问题在中观尺度上得到了最好的描述，在中观尺度上，量子效应可以忽略不计，温度也不大。这些问题包括电子在小颗粒阵列之间的传输、多孔介质中的粘性流体以及超导体中的磁涡流。由PI和合作者开发的具有守恒定律的塑性流动的各向异性粗粒度模型将被详细研究。除了研究这些系统中的随机性之外，PI还将模拟设计的准周期系统对交流驱动器的响应，例如可能用胶体粒子实现的响应。更广泛的影响：该项目的具体科学目标的进展将与更广泛的利益密切相关。PI将培养研究生和博士后研究人员，重点关注直接模拟、高级算法和凝聚态物理之间的重叠。要研究的模型是无序材料的原型，并为广泛的系统提供了物理图像，包括无序存在的量子临界点和生物聚合物的折叠。在理解无序系统的静力学和动力学方面的进展，包括域结构和迟滞，最终将应用于材料开发，包括磁存储器。这项工作将加强计算机科学（组合优化算法及其运行时间）和物理学（长度尺度和动态无限维材料）之间的联系。PI开发的计算机程序将被广泛使用。PI通过与凝聚态物理相关的演讲和活动，积极与当地社区分享科学。摘要：本理论项目将探索性质由无序决定的材料和凝聚态系统。经典固态材料的特点是原子排列整齐。然而，大多数材料都有一定程度的无序性，有些材料的独特性质归功于无序性的存在。本研究将主要使用数值方法（计算）来研究无序对当前感兴趣的各种材料的影响。所使用的数值方法与所描述的物理图像之间的联系可以导致计算机代码的进步，从而具有更广泛的应用。这些联系也将继续进行。