CDS&E: A New Approach for Determining the Free Energy and Absolute Mobility of Flat, Curved, and Moving Interfaces

CDS

• 批准号: 1710186
• 负责人: Elizabeth Holm
• 金额: $ 39.3万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-05-01 至 2022-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1710186&HistoricalAwards=false
• 关键词: CDS& New; Approach; Determining; Free

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education on interfaces in materials which may be in different states. In the natural world, materials often spontaneously change their state. For example, on a warm day, solid ice melts to become liquid water. However, ice cubes don't melt all at once; instead, they melt at the surface. Scientists study the process of melting, therefore, by understanding the properties of the surface between the solid and liquid, termed the solid/liquid interface, and the processes that take place there.The characteristics of the solid/liquid interface depend on the molecular structure, and molecules are very small, very fast, and very difficult to control. In this project, the research team will develop a new computer simulation method that slows down the molecular motions in a controlled manner so that the team can extract information about the interfacial properties and processes in solids and liquids. The results will help scientists better understand melting and freezing, which is important in metal casting and in 3D printing. In addition, the research team will study solid/solid interfaces, which occur in diverse materials from batteries to steel, and solid/vapor interfaces, which influence the production of electronic materials.Computer simulations of this type are increasingly important to support scientific and technological advancement. To prepare the materials science workforce in these new methods, this project will help train bachelors, masters, and doctoral students in the principles of computational materials science. Furthermore, to maximize the impact of this work, the methods and results of this project will be available to all interested scientists.TECHNICAL SUMMARYThis award supports theoretical and computational research and education on interfaces in materials which may be in different states. An interface is a planar defect that occurs at the intersection of materials that differ in state, phase, crystal orientation, magnetic spin, atomic ordering, or any other structural parameter. Because interfaces represent a disruption in electronic, magnetic, or atomic structure, they contribute a positive free energy to the system. Thus, if an interface is mobile, it will move so as to minimize the total system free energy. When an interface moves, it interacts with other interfaces, with internal and external fields, and with geometric boundary conditions, continuously altering its configuration. As its local environment evolves, the interface structure, shape, and rate-limiting motion mechanism may change as well. Such collective interactions ensure that in real materials, interfaces rarely attain metastable equilibrium configurations. Because interfaces mediate the thermal, electrical, mechanical, optical, chemical, and functional properties of materials, materials scientists study their thermodynamics and kinetics. However, nearly all methods are limited to interfaces that are in metastable equilibrium configurations and cannot be applied to the mobile, evolving interfaces that occur during material processing. The goal of this work is to develop a new approach for obtaining the true free energy and absolute mobility of interfaces at and away from equilibrium in order to enable physical discovery, provide deeper understanding of mechanisms and outcomes, and link to mesoscale material processes.A new method for calculating finite temperature interfacial free energy and mobility is proposed. Termed driving force balanced molecular dynamics (DFB-MD) method, it relies on balancing two or more known driving forces, yielding a system of equations that can be solved for interface free energy and mobility. One driving force is synthetic, thus imposed upon the system; the other(s) may include curvature, chemical, stress, magnetic, defect, or other contributions. Because the interface need not be in an equilibrium configuration, the properties of curved and/or moving boundaries can be obtained. These materials properties may then be used to inform materials models at larger length and time scales or to interpret experimental observations.The DFB-MD approach may be generalized to other system geometries, driving forces, and processes. By defining an appropriate order parameter and applying a known excess energy based on that parameter, the motion of many types of interfaces - potentially including other defects - may be altered. This ability to influence the motion of a moving interface has the potential to offer insight into a number of open problems involving complex processes, including dislocation motion, grain growth and coarsening, precipitation, crystal growth, and vacancy formation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要该奖项支持对可能处于不同状态的材料界面的理论和计算研究及教育。在自然界中，材料经常会自发地改变其状态。例如，在温暖的日子里，固体冰融化成液态水。然而，冰块不会一下子全部融化；而是会立即融化。相反，它们在表面融化。因此，科学家通过了解固体和液体之间的表面（称为固/液界面）的特性以及在那里发生的过程来研究熔化过程。固/液界面的特性取决于分子结构，而分子非常小、速度非常快且非常难以控制。在这个项目中，研究团队将开发一种新的计算机模拟方法，以受控方式减慢分子运动，以便团队能够提取有关固体和液体界面特性和过程的信息。研究结果将帮助科学家更好地了解熔化和冷冻，这对于金属铸造和 3D 打印非常重要。此外，研究小组还将研究从电池到钢铁等多种材料中出现的固体/固体界面，以及影响电子材料生产的固体/蒸气界面。此类计算机模拟对于支持科学技术进步越来越重要。为了使用这些新方法培养材料科学人才，该项目将帮助培训学士、硕士和博士生了解计算材料科学原理。此外，为了最大限度地发挥这项工作的影响，该项目的方法和结果将提供给所有感兴趣的科学家。技术摘要该奖项支持对可能处于不同状态的材料界面的理论和计算研究及教育。界面是一种平面缺陷，发生在状态、相、晶体取向、磁自旋、原子排序或任何其他结构参数不同的材料的交叉处。由于界面代表了电子、磁性或原子结构的破坏，因此它们为系统贡献了正的自由能。因此，如果界面是可移动的，它将移动以最小化总系统自由能。当界面移动时，它与其他界面、内部和外部场以及几何边界条件相互作用，不断改变其配置。随着局部环境的演变，界面结构、形状和限速运动机制也可能发生变化。这种集体相互作用确保在实际材料中，界面很少达到亚稳态平衡配置。由于界面介导材料的热、电、机械、光学、化学和功能特性，因此材料科学家研究它们的热力学和动力学。然而，几乎所有方法都仅限于处于亚稳态平衡配置的界面，并且不能应用于材料加工过程中发生的移动、演变的界面。这项工作的目标是开发一种新方法来获得平衡态和非平衡态界面的真实自由能和绝对迁移率，以便实现物理发现，提供对机制和结果的更深入理解，并与介观材料过程联系起来。提出了一种计算有限温度界面自由能和迁移率的新方法。称为驱动力平衡分子动力学 (DFB-MD) 方法，它依赖于平衡两个或多个已知驱动力，产生可以求解界面自由能和迁移率的方程组。一种驱动力是合成的，因此强加于系统；其他可能包括曲率、化学、应力、磁性、缺陷或其他贡献。因为界面不需要处于平衡配置，所以可以获得弯曲和/或移动边界的属性。然后，这些材料特性可用于为更大长度和时间尺度的材料模型提供信息，或解释实验观察结果。DFB-MD 方法可推广到其他系统几何形状、驱动力和过程。通过定义适当的阶次参数并基于该参数应用已知的过剩能量，可以改变许多类型界面的运动（可能包括其他缺陷）。这种影响移动界面运动的能力有可能为涉及复杂过程的许多开放性问题提供深入的见解，包括位错运动、晶粒生长和粗化、沉淀、晶体生长和空位形成。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Learning the grain boundary manifold: tools for visualizing and fitting grain boundary properties

• DOI: 10.1016/j.actamat.2020.05.024
• 发表时间: 2020-08-15
• 期刊: ACTA MATERIALIA
• 影响因子: 9.4
• 作者: Chesser, I;Francis, T.;Holm, E. A.
• 通讯作者: Holm, E. A.

A geodesic octonion metric for grain boundaries

• DOI: 10.1016/j.actamat.2018.12.034
• 发表时间: 2019-03-01
• 期刊: ACTA MATERIALIA
• 影响因子: 9.4
• 作者: Francis, Toby;Chesser, Ian;De Graef, Marc
• 通讯作者: De Graef, Marc

Distinct driven steady states emerge from diverse initial textures in rolled nanocomposites

• DOI: 10.1016/j.actamat.2019.10.058
• 发表时间: 2020-01
• 期刊: Acta Materialia
• 影响因子: 9.4
• 作者: I. Chesser;E. Holm;M. Demkowicz

A taxonomy of grain boundary migration mechanisms via displacement texture characterization

• DOI: 10.1016/j.actamat.2021.117425
• 发表时间: 2021-08
• 期刊: Acta Materialia
• 影响因子: 9.4
• 作者: I. Chesser;B. Runnels;Elizabeth A. Holm

A continuum thermodynamic framework for grain boundary motion

• DOI: 10.1016/j.jmps.2019.103827
• 发表时间: 2020-04
• 期刊: Journal of The Mechanics and Physics of Solids
• 影响因子: 5.3
• 作者: I. Chesser;Tingting Yu;C. Deng;E. Holm;B. Runnels