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各自的例子。胶带用于从大块晶体上剥离层。一个大的二维晶体库可以分离和制备，每一个都有其独特的特征。人们设想通过层层堆叠将孤立的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，原子平面内部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更高的可靠性。该研究本质上是多学科的，将力学与材料科学和多尺度计算建模相结合。本项目培养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仿真模型打包成用户友好的软件，并使更广泛的研究社区可以访问这些软件。这一努力将促进和刺激机械师与材料科学家、物理学家和化学家在纳米技术这一新领域的合作研究。分层晶体支持在块状晶体中不存在或不重要的新缺陷。最近的一项研究表明，层状晶体中的表面位错与块状晶体中的常规位错相比，具有明显的波纹形态。这种缺陷被称为波纹定位。这条线缺陷是直的，窄的，晶体取向的，高度可移动的。研究小组假设，当波纹位置扫过二维晶体平面时，可能会导致层内缺陷的重排和层间吸收。因此，它可以作为缺陷收集器和清洁器。为了验证这一假设，本项目试图定义一套多尺度模型来描述波纹与层内缺陷和层间吸收之间的相互作用。研究结果将为波纹定位介导的缺陷重排和去除提供基础指导。该研究项目将为三维层状异质结构的缺陷控制和工程基础提供一个新的范例。

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.