Multiscale Modeling of Defect Rearrangement and Removal in 2D Layered Crystals

二维（2D）晶体由单层或几层原子组成。石墨烯和二硫化钼是相应的实例。胶带用于从大块晶体上剥离层。可以分离和制备一个大型的2D晶体库，每个晶体都有其独特的特性。已经设想通过逐层堆叠将孤立的2D晶体重新组装成3D层状结构。通过合理选择原子层和堆叠顺序，这些垂直层状晶体可以具有特殊的多功能特性，用于组合和耦合机械，光学和电子应用。然而，原子平面内的缺陷和相邻原子平面之间的缺陷会显著降低材料的性能。该奖项支持对层状晶体中普遍存在的一类新缺陷及其与其他原子缺陷和杂质的相互作用的基础研究。这项研究的结果将为处理缺陷的工程过程提供见解，并导致从层状晶体中去除缺陷。这最终将导致材料具有增强的可靠性。这项研究是多学科的性质，接口力学与材料科学和多尺度计算建模。在这个项目下培训的研究生和本科生将接触到多学科的研究环境。软件共享计划包括将模拟模型打包成用户友好的软件，并使更广泛的研究界可以使用这些软件。这一努力将促进和刺激机械学家和材料科学家、物理学家和化学家在纳米技术这一新领域的合作研究。层状晶体支持大块晶体中不存在或不重要的新类型缺陷。最近的一项研究表明，层状晶体中的表面位错呈现出与体相晶体中的传统位错截然不同的波纹形态。这种缺陷被称为ripplocation。该线缺陷是直的、窄的、晶体学取向的并且是高度移动的。该团队假设，当涟漪位置扫过2D晶体平面时，它可能会导致层内缺陷和层间吸收的重新排列。因此，它可以用作缺陷收集器和清洁器。为了验证这一假设，本项目旨在定义一组多尺度模型，用于表征ripplocations和层内缺陷和层间吸收之间的相互作用。研究结果将为ripplocation介导的缺陷重排和去除提供基础指导。该研究项目将在缺陷控制和3D分层异质结构工程基础方面开创一种新的范例。

Two-dimensional (2D) crystals consist of a single layer or a few layers of atoms. Graphene and Molybdenum disulfide are respective examples. Adhesive tapes are used to peel layers off from bulk crystals. A large library of 2D crystals can be isolated and prepared, each with its unique character. It has been conceived to reassemble the isolated 2D crystals into 3D layered structures through layer-by-layer stacking. With rationally chosen atomic layers and stacking sequence, these vertically layered crystals can possess exceptional multifunctional properties for combined and coupled mechanical, optical, and electronic applications. However, defects within the atomic planes themselves and between the neighboring atomic planes can significantly degrade the materials performance. This award supports fundamental research on a new class of defects ubiquitous in layered crystals and their interactions with other atomic defects and impurities. Results from this research will provide insights into engineering processes dealing with defects and leading to the removal of defects from the layered crystals. This ultimately would lead to materials with enhanced reliability. The research is multidisciplinary in nature, interfacing mechanics with materials science and multiscale computational modeling. Graduate and undergraduate students trained under this project will be exposed to the multidisciplinary research environment. The software-sharing plan involves packaging the simulation models into user-friendly software and make these accessible to the broader research community. This effort will facilitate and stimulate collaborative research between mechanicians and materials scientists, physicists, and chemists in this new field of nanotechnology.Layered crystals support new classes of defects that are absent or unimportant in bulk crystals. A recent study has demonstrated that surface dislocations in layered crystals exhibit a rippling morphology in distinct comparison to conventional dislocations in bulk crystals. This defect is termed ripplocation. This line defect is straight, narrow, crystallographically oriented, and highly mobile. The team hypothesizes that as a ripplocation sweeps through the plane of the 2D crystals, it may cause rearrangement of intralayer defects and interlayer absorbates. It thus might function as defect collector and cleaner. To test this hypothesis, this project seeks to define a set of multiscale models for characterizing the interactions between ripplocations and the intralayer defects and interlayer absorbates. Research results will provide a fundamental guidance for ripplocation-mediated defect rearrangement and removal. The research project will initiate a new paradigm in the control of defects and the fundamentals for engineering of 3D layered heterostructures.