Collaborative Research: Mesoscopic Defect Field Interactions in Materials with High Number Density of Interfaces

晶体材料的变形行为非常复杂，因为描述其结构组成的长度尺度的层次结构。界面在这些不同的长度尺度上连接不同的晶体结构或材料相。晶体缺陷与界面的相互作用是导致材料在应用范围内的突现行为的主要原因。通过多个尺度直到日常应用的更高尺度的缺陷和接口的集体相互作用一直是极具挑战性的实验解决方案，并且也没有使用计算机模拟来捕捉到所需的复杂性。这是理解复杂材料行为的一个重大障碍，在这种情况下，高密度的特定界面有助于实现优异的功能和/或机械性能。这项研究旨在通过研究超晶格和超材料来解决这一挑战，开发并进一步推进原子到连续介质的尺度方法。预计这项研究将极大地促进材料力学和计算材料科学领域的发展，并对迅速发展的计算材料设计领域产生相应的影响，促进国民的健康、繁荣和福祉。这项工作预计还将通过对本科生进行高性能计算培训、研究生课程改进以及向更广泛的社区传播代码来产生更广泛的影响。该项目还将接触到来自代表不足的群体的学生。超晶格和超材料代表了两个新兴的材料系统，它们的特殊性质来自结构而不是组成。超晶格和超材料具有有序的周期性界面和结构，为系统研究界面在缺陷结构演化中的集体作用提供了模型系统。这项合作工作的目标是通过使用先进的并行原子-连续(CAC)方法研究这类特殊的材料系统来展示界面和缺陷对机械性能的集体作用。预计这项研究将确定主导的变形机制以及控制材料行为和潜在机制的关键结构变量，探索材料从延性行为向脆性行为转变的临界长度尺度或结构参数，并调查控制这些材料系统中塑性流动和断裂行为的基本现象。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Deformation behavior of crystalline materials is highly complex, owing to a hierarchy of length scales that describes their structural makeup. Interfaces link distinct crystal structures or material phases at these various length scales. The interactions of crystalline defects with interfaces are chiefly responsible for the emergent material behavior at the application scale. The collective interactions of defects and interfaces through multiple scales up to the higher scale of everyday applications have been extremely challenging to resolve experimentally and have also not been captured using computer simulations to the desired sophistication. This is a significant obstacle to the understanding of the behavior of complex materials, where high density of specific interfaces is instrumental in achieving superior functional and/or mechanical properties. This research aims to address this challenge through the study of superlattices and metamaterials by exploiting and further advancing an atomistic-to-continuum scale method. It is expected that this research will significantly promote the fields of mechanics of materials and computational materials science, with commensurate impact on the rapidly developing field of computational materials design, which will advance national health, prosperity, and welfare. This work is also expected to have substantial broader impact through training of undergraduate students in high-performance computing, graduate curriculum enhancements, and dissemination of codes to the wider community. The project will also reach out to engage students from underrepresented groups.Superlattices and metamaterials represent two emerging material systems that derive their exceptional properties from structure rather than composition. With their well-ordered periodic interfaces and structure, superlattices and metamaterials provide model systems amenable to systematic study of the collective role of interfaces on evolving defect structures. The goal of this collaborative effort is to demonstrate the collective role of interfaces and defects on mechanical properties by studying this special class of material systems by using an advanced Concurrent Atomistic-Continuum (CAC) approach. It is expected that this research will identify the dominant deformation mechanisms as well as the key structural variables that control the materials behavior and the underlying mechanisms, explore the critical length scale or structural parameters at which the materials exhibit a transition from ductile to brittle behavior, and investigate the fundamental phenomena that control the plastic flow and fracture behaviors in these material systems.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.