NSF/DMR-BSF: Quantum Materials from Geometric and Dimensionality Design

该奖项支持理论和计算研究和教育，以提高将特定功能设计到材料中的能力。材料的工程特性使其成为技术关键，例如特殊的光学，结构或磁性功能，通常通过控制化合物的化学成分来实现。PI将研究一种较少探索的策略-通过将简单的已知构建块材料组装成各种几何形状而不改变其成分来实现目标功能。例如，基于量子力学的理论计算表明，围绕硅核的硅和锗的同心交替壳的设计可以提供组成构建块完全不存在的新颖光学特性。类似地，由元素钼和被称为硫属化物的一类元素中的任何一种制成的针的设计组件可以提供在更常见的三维几何形状中未知的电子物质的新状态。通过将基于量子力学的固体材料计算机模拟与材料设计原理相结合，PI旨在开发新的方法来预测材料的新兴特性，例如独特的光学和磁性。该项目将受益于与特拉维夫大学实验人员的合作。研究生和博士后将被鼓励通过科罗拉多大学的一个项目来发展大学水平的教学经验。该项目包括面向广大受众的外联研讨会活动。技术总结该奖项支持理论和计算研究和教育，以提高设计具有特定功能的材料的能力。在历史上，对获得材料优异物理性能的追求涉及合成新的、复杂性不断增加的单个化合物。但并非所有这些化合物都能提供技术人员希望在特定设备中应用的最佳性能。最近的一种替代方法是从超结构中寻求所需的功能，以及探索降低维度，使用本身可能缺乏有趣特性的常见化合物构建块。PI建立在他最近的几何和维度设计工作的基础上，以获得大大取代或甚至在质量上不存在于单个化合物构建块中的新特性。该方法涉及寻找特定的超结构模式或具有特定的约化对称性的多晶型物，这些对称性提供了不寻常的涌现量子特性。在这个通常未探索的研究领域的具体探索包括：（i）从间接带隙Si和Ge组分和Giant Rashba效应设计核-多壳1D超结构中的直接带隙，（ii）研究金属和绝缘性质的共存，以及过渡金属单硫族化物的1D多晶型物中新电子态的出现，（iii）通过亚稳态或内部电场的能量稳定化，通过拓扑平凡的普通分量的超结构来寻找拓扑系统。超结构提供的可能配置的数量是如此之大，以至于高通量的方法，实验或计算，是不切实际的。PI将把这种纳米结构作为一个设计问题来处理，使用功能驱动的搜索和发现，将（a）电子结构方法与（B）稳定性筛选和（c）必要时的进化搜索相结合，以确定具有稳定性和有趣目标特性的“神奇构型”。超结构将导致更好地理解有趣的量子特性的关键使能因素，以及创造新功能的实际优势。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education to advance the capability to design specific functionality into materials. Engineering properties of materials to make them technology critical, such as special optical, structural or magnetic functionalities, is generally achieved by controlling the chemical composition of compounds. The PI will investigate a much less explored strategy - attaining target functionalities by assembling simple, known building block materials into various geometric shapes without changing their compositions. For example, quantum mechanics-based theory calculations suggest that the design of concentric alternate shells of Silicon and Germanium around a core of silicon can deliver novel optical properties that are altogether absent from the constituent building blocks. Similarly, a designed assembly of needles made from the element Molybdenum and any one of a class of elements known as chalcogenides can deliver a new state of electronic matter that is unknown in more common three-dimensional geometric shapes. By combining computer simulations of solid materials based on quantum mechanics with materials design principles, the PI aims to develop novel ways to predict emerging properties of materials, such as unique optical and magnetic properties. This project will benefit from collaboration with experimentalists at Tel Aviv University. Graduate students and postdocs will be encouraged to develop college-level teaching experience through a program at the University of Colorado. The project includes an outreach seminar activity to a broad audience.TECHNICAL SUMMARYThis award supports theoretical and computational research and education to advance the capability to design materials with specific functionality. The quest for attaining outstanding physical properties of materials historically involved synthesis of new individual compounds of ever increasing complexity. But not all such compounds have delivered the optimal properties technologists wished to have for applications in particular devices. A recent alternative has been to seek desired functionalities from superstructuring, as well as exploration of reduced dimensionality, using common compound building blocks that by themselves may lack interesting properties. The PI builds upon his recent work on geometric and dimensionality design to obtain emergent properties that greatly supersede or are even qualitatively absent from those attainable from the individual compound building blocks. The approach involves the search for specific superstructure patterns or polymorphs with specific reduced symmetries that deliver unusual, emergent quantum properties. Specific explorations within this generally unexplored research field include: (i) engineering a direct band gap in core-multi-shell 1D-superstructures from indirect gap Si and Ge components and the Giant Rashba effect, (ii) investigating the coexistence of metallic and insulating properties, and the emergence of novel electronic states in 1D-polymorph of transition-metal mono-chalcogenides, (iii) finding topological systems by superstructuring of topologically trivial ordinary components through energy stabilization of metastable states or internal electric fields. The number of possible configurations afforded by superstructuring is so large that high-throughput approaches, experimental or computational, are impractical. The PI will approach such nanostructures as a design problem, using functionality-driven search and discovery that combines (a) electronic structure methods with (b) screening for stability and (c) evolutionary search where needed, to identify the "magic configurations" that have both stability and interesting target properties. Superstructuring will lead to better understanding of the critical enabling factors of the intriguing quantum properties, as well as have the practical advantage of creating new functionalities.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.