FRG: Predictive Computational Modeling of Two-Dimensional Materials Beyond Graphene: Defects and Morphologies

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NONTECHNICAL SUMMARYThe Division of Materials Research and the Division of Mathematical Sciences contribute funds to this award. It supports interdisciplinary research and educational activities in computational materials science, with a focus on the growth of two-dimensional (2D) semiconducting materials. While graphene is the best-known 2D material, it is limited in device application due to its high conductivity. More recent research has focused on 2D semiconducting materials, which can be manipulated to block or permit current flow. These research activities have been primarily based on experimental explorations due to a gap in the fundamental understanding in what determines their structures and properties. This project aims to help fill this gap by developing a model for the growth of these systems based on the phase field crystal modeling approach. This approach allows researchers to study materials involving tiny structures as small as atoms. The team of researchers will develop, parameterize, and validate a phase field crystal model for 2D semiconducting materials, which can be used improve the synthesis process of 2D materials and their assembly. Simulations will also be used to examine the structure of these materials and associated defects at the atomic level. Educational activities include courses on crystal growth for high school students, proposed as part of the California State Summer School for Mathematics and Science at UC Irvine, engaging with Science Olympiad, and other STEM events. These activities will help develop the future generation of mathematicians, scientists and engineers. Graduate students will receive interdisciplinary training and will present their findings at conferences, which will enhance their educational experience. The team shall also act as a resource for the research community by distributing the codes that are developed and by organizing symposia on phase field crystal models at national meetings.TECHNICAL SUMMARYThe Division of Materials Research and the Division of Mathematical Sciences contribute funds to this award. It supports interdisciplinary research and educational activities in computational materials science, with a focus on the growth of two-dimensional (2D) semiconducting materials. The recent discovery of two-dimensional (2D) semiconducting materials such as MoS2 and MoSe2 has intensified the research efforts in these materials. These materials exhibit unique properties due to the 2D confinement, but they, unlike graphene, also possess the ability to switch between conducting and insulating states, offering a potential to yield revolutionary new technologies. The research efforts have been primarily based on experimental exploration based on various synthetic routes, and significant gaps exist in the fundamental understanding of what determine their bulk and defect structures and morphologies, as well as how they influence their properties. Due to the small length scale involved, computational modeling is essential for developing such understanding. Phase field crystal (PFC) modeling is uniquely suited for this problem because of its ability to resolve atomic-scale structure and its extended time-scale comparable to those associated with synthesis. This multidisciplinary project addresses the challenge of understanding multiscale phenomena associated with the formation of nanostructures by exploiting recent developments in PFC models, which follow the dynamics of individual atoms over diffusive time scales. Originating from classical density functional theory, the PFC method naturally incorporates elastic and plastic deformations as well as crystalline defects. The team of materials scientists and a mathematician will develop a new PFC-based computational methodology for modeling the structure and the synthesis of two-dimensional, multicomponent materials. The models will be parameterized and validated with the aid of atomistic simulations and experimental results. Defects such as grain boundaries, which must be controlled in device applications, will be examined. The computational tools will build on the efficient numerical algorithms developed under previous funding and tailor it to the new models and will be disseminated through repositories such as GitHub. These tools will provide a framework for the computational discovery of the fundamental mechanisms underlying synthesis of 2D materials, their assembly, and their atomic-scale structure. Educational activities include courses on crystal growth for high school students, proposed as part of the California State Summer School for Mathematics and Science at UC Irvine, engaging with the Science Olympiad, and other STEM events. These activities will help develop the future generation of mathematicians, scientists and engineers. Graduate students will receive interdisciplinary training and will present their findings at conferences, which would enhance their educational experience. The group shall also act as a resource for the research community by organizing symposia on phase field crystal models at national meetings.