Designing complex chalcogenides through building block approach

第1部分：非技术概述器械的性能取决于其制造材料的性能。例如，手机需要一个高效的锂离子电池来运行更长的时间而不需要充电，而高清电视需要高质量的荧光粉（颜色产生材料）来获得高分辨率的颜色。目前，科学家们通过直觉和艰苦的试验和错误的结合来实现和改善设备中材料的预期性能，导致发现新的、更好的和/或更便宜的材料的速度很慢。为新材料提出合理的设计原则可以加速这些发现。在美国国家科学基金会材料研究部固态和材料化学项目的支持下，来自密苏里大学的团队通过理论预测辅助实验，以更合理和可预测的方式开发新材料。该团队合成并使用固定的分子单位来生产具有定制性能的新材料。这些分子单位或积木就像乐高积木或砖块，有各种形状和大小，可以以不同的和可预测的方式精确连接。通过这项NSF奖，该团队准备了高导电性的固体离子导体，这是实现全固态锂离子电池所需的，这比目前的技术要安全得多。密苏里理工大学的本科生和研究生参与了这个项目，并接受了在物理和化学领域工作的培训。从这个跨学科项目中获得的知识被整合到本科和研究生水平的课程中。此外，向高中学生和教师展示这些材料在电池中的应用的讲习班旨在教育和吸引那些在科学方面代表性不足的少数民族背景的学生。定向合成具有理想性能的材料是固体材料化学领域追求的目标。该项目由美国国家科学基金会材料研究部固态和材料化学项目资助，通过涉及碱金属硫金属酸盐和金属卤化物的复分解反应，开发了直接合成多硫族化合物的方法。它是基于这样的假设，即在这些反应中，初始反应物中存在的金属chalcomallate构建块在目标化合物中保持完整。含有不同负电荷和共价程度的主族元素的大量金属chalcom金属酸盐单元的可用性使它们成为合成具有所需应用的材料的理想选择。通过选择合适的积木和金属离子组合，可以合理设计出与磁性、离子传导和氧化还原性能相关的有用性能的材料。本研究的重点是创造更稳定的固体离子导体和氧化还原活性硫系晶格。实验合成工作与预测密度泛函理论（DFT）模拟可能的结构和组成的热力学稳定性紧密结合。DFT计算与化学直觉一起从组成空间中选择最有希望的合成候选者，然后将其合成以验证理论预测。这种合理合成复杂硫族化合物的协同实验-理论方法可转化为具有广泛应用的各种其他材料系统，包括储能，光伏，热电和固态照明。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。

PART 1: NON-TECHNICAL SUMMARY The performance of a device is dependent on the performance of the materials it is made of. For example, cell phones need a high efficiency lithium-ion battery to run longer without recharging, while HDTVs need good quality phosphors (color generating materials) for high resolution color. Scientists currently achieve and improve the desired properties of the materials in devices by a combination of intuition and painstaking trial and error, resulting in slow rate of discoveries of the new, better and/or cheaper materials. Coming up with rational design principles for new materials can speed-up these discoveries. With support from NSF's Solid State and Materials Chemistry Program in the Division of Materials Research, the team from Missouri S&T develops new materials in a more rational and predictive manner by performing experiments aided by theoretical predictions. The team synthesizes and uses fixed molecular units to produce new materials with tailored properties. These molecular units or building blocks are like legos or bricks that come in various shapes and sizes and can be precisely connected in different and predictable ways. Through this NSF award the team prepares highly conducting solid ion conductors that are needed to enable all-solid-state lithium ion batteries, which are much safer than current technologies. Undergraduate and graduate students from Missouri S&T are involved in carrying out this project and are getting trained to work in the realm of physics and chemistry. Knowledge acquired from this interdisciplinary project is integrated into undergraduate and graduate level courses. Additionally, workshops demonstrating the application of these materials in batteries to high school students and teachers are designed to educate and interest students with an underrepresented minority background in science.PART 2: TECHNICAL SUMMARY Directed synthesis of materials possessing desired property is a sought-after goal in solid state materials chemistry. This project, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, develops direct synthesis methods for multinary chalcogenides via metathesis reactions involving alkali chalcometallates and metal halides. It is based on the hypothesis that in these reactions, chalcometallate building blocks present in the starting reactants remain intact in the targeted compounds. The availability of large number of chalcometallate units containing main group elements with varying negative charge and degree of covalence makes them ideal for the synthesis of materials with desired applications. By choosing appropriate combinations of building blocks and metal ions materials that can generate useful properties related to magnetism, ion conduction and redox properties are rationally designed. The focus of this study is to create more stable solid ion conductors and redox active chalcogenide lattices. Experimental synthesis efforts are performed in tight integration with the predictive Density Functional Theory (DFT) simulations of the thermodynamic stability of the possible structures and compositions. DFT calculations are used together with the chemical intuition to down-select the most promising candidates for synthesis out of the compositional space, which are then synthesized to validate the theoretical prediction. This synergetic experimental-theoretical approach to rationally synthesize complex chalcogenides is translatable to a wide variety of other materials systems with wide range of applications, including energy storage, photovoltaics, thermoelectrics, and solid state lighting.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.