Harnessing unconventional structural degrees of freedom to design new hybrid layered perovskites

该奖项支持理论和计算研究和教育，旨在使用计算机预测和理解一类混合有机-无机氧化物材料的性质。先进材料塑造了现代生活的许多方面，从智能电子产品到高速通信和可再生能源。尽管如此，发现具有技术上有用特性的材料是一个缓慢而困难的过程。基于物理基本定律的先进计算技术的发展，以及计算机能力的巨大增长，已经改变了科学家研究、发现和设计特定应用材料的方式。例如，尚未合成的材料的性质可以用计算机模拟来预测和研究，这样实验学家就可以把精力集中在最有前途的材料族或成分上。在这个项目中，PI将研究一类混合有机-无机氧化物材料的化学成分与其最低能量结构和物理性质之间的关系，例如它们产生自发极化的能力，这种自发极化可以通过施加外电场来切换。目的是发展一种化学上直观的理论，实验学家可以用它从大量的候选材料中快速过滤出有前途的材料。通过与实验人员的密切合作，计算机模拟的结果将得到验证。该奖项还将支持(1)通过在PI小组和英国牛津大学无机化学实验室之间建立一个交流计划，以促进理论/计算小组和实验小组之间的合作和知识/技能交流，为PI的科学劳动力发展做出努力；（ii）通过在课堂教学和课堂设计中引入并进一步发展循证技术，帮助学生制定有效的学习策略，在PI所在机构开展课程开发工作。该奖项支持理论和计算研究，旨在阐明一系列有机-无机Dion-Jacobson杂化氧化物中铁电性和磁电性结构基础的基本物理和化学因素。有机-无机杂化钙钛矿具有独特的结构自由度；它们是非常规的，因为它们在完全无机的对应物中不被观察到，甚至可能被禁止。然而，与杂化卤化物钙钛矿相比，杂化氧化物钙钛矿尚未得到详细的研究。此外，与无机钙钛矿相比，将混合有机-无机层状钙钛矿氧化物中特定结构扭曲的物理机制与键合和晶体化学联系起来的化学直观、微观理论的发展几乎不存在。在这个项目中，利用对称原理、第一性原理密度泛函理论计算和晶体化学模型，PI将揭示晶体化学的基本知识和铁电的物理机制，这将使混合有机-无机层状钙钛矿氧化物的合理设计成为可能。该研究项目的成功完成有望为设计和发现新型混合有机-无机层状钙钛矿建立一个新的材料平台。该奖项还将支持(1)通过在PI小组和英国牛津大学无机化学实验室之间建立一个交流计划，以促进理论/计算小组和实验小组之间的合作和知识/技能交流，为PI的科学劳动力发展做出努力；（ii）通过在课堂教学和课堂设计中引入并进一步发展循证技术，帮助学生制定有效的学习策略，在PI所在机构开展课程开发工作。该奖项反映了美国国家科学基金会的法定使命，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 that aims to use computers to predict and understand the properties of a class of hybrid organic-inorganic oxide materials. Advanced materials shape many of the aspects of modern life, from smart electronics to high-speed communications and renewable energy sources. Despite this, the discovery of materials with technologically useful properties is a slow and difficult process. The development of advanced computational techniques, based on the fundamental laws of physics, together with vast increases in computer power, have transformed the way scientists investigate, discover and design materials for particular applications. For example, the properties of as-yet unsynthesized materials can be predicted and studied using computer simulations, such that experimentalists can focus their efforts on the most promising materials families or compositions. In this project, the PI will investigate the relationship between the chemical composition of a class of hybrid organic-inorganic oxide materials and their lowest-energy structure and physical properties, such as their ability to develop spontaneous polarization that is switchable by applying external electric fields. The aim is to develop a chemically intuitive theory that experimentalists can use to quickly filter promising materials out of the vast number of candidate materials. The results of computer simulations will be validated through close collaboration with experimentalists.This award will also support (i) the PI's scientific workforce development efforts by establishing an exchange program between the PI's group and the Inorganic Chemistry Laboratory at the University of Oxford, UK, with an aim to promote collaboration and knowledge/skills exchange between theoretical/computational groups and experimental groups, and (ii) curricular development efforts at the PI’s institution by introducing and further developing evidence-based techniques into classroom instruction and class design to assist students in formulating effective learning strategies.TECHNICAL SUMMARYThis award supports theoretical and computational research with an aim to elucidate the fundamental physical and chemical factors underlying the structural basis of ferroelectricity and magnetoelectricity in a series of hybrid organic-inorganic Dion-Jacobson oxides. Hybrid organic-inorganic perovskites can exhibit unique structural degrees of freedom; they are unconventional in the sense that they are not observed, and may even be forbidden, in their fully inorganic counterparts. However, in contrast with hybrid halide perovskites, hybrid oxide perovskites have not been explored in detail. In addition, in comparison with inorganic perovskites, the development of a chemically intuitive, microscopic theory that connects the physical mechanisms of particular structural distortions in hybrid organic-inorganic layered perovskite oxides to bonding and crystal chemistry is almost non-existent. In this project, using symmetry principles, first-principles density functional theory calculations and crystal chemical models, the PI will uncover the fundamental knowledge of crystal chemistry and physical mechanisms of ferroelectricity that will enable rational design of hybrid organic-inorganic layered perovskite oxides. The successful completion of this research program is expected to result in the establishment of a new materials platform for designing and discovering novel hybrid organic-inorganic layered perovskites.This award will also support (i) the PI's scientific workforce development efforts by establishing an exchange program between the PI's group and the Inorganic Chemistry Laboratory at the University of Oxford, UK, with an aim to promote collaboration and knowledge/skills exchange between theoretical/computational groups and experimental groups, and (ii) curricular development efforts at the PI’s institution by introducing and further developing evidence-based techniques into classroom instruction and class design to assist students in formulating effective learning strategies.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.