Designing complex chalcogenides through building block approach

第1部分：非技术概述设备的性能取决于其所用材料的性能。例如，手机需要高效率的锂离子电池才能在不充电的情况下运行更长时间，而高清电视需要高质量的荧光粉(生色材料)来实现高分辨率的色彩。科学家目前通过直觉和艰苦的试错相结合的方式，在设备中实现并改进了材料的预期特性，导致发现新的、更好的和/或更便宜的材料的速度很慢。提出新材料的合理设计原则可以加快这些发现的速度。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，来自密苏里州S与技术公司的团队通过在理论预测的辅助下进行实验，以更合理和更具预测性的方式开发新材料。该团队合成并使用固定的分子单元来生产具有定制性能的新材料。这些分子单元或积木就像乐高积木或积木，形状和大小各不相同，可以以不同和可预测的方式精确连接。通过这项NSF奖，该团队准备了实现全固态锂离子电池所需的高导电性固体离子导体，这种电池比目前的技术安全得多。密苏里州S大学的本科生和研究生参与了这一项目的实施，并正在接受在物理和化学领域工作的培训。从这个跨学科项目获得的知识被整合到本科生和研究生水平的课程中。此外，向高中生和教师展示这些材料在电池中的应用的研讨会旨在教育和吸引在科学中代表少数族裔背景的学生。第二部分：技术概述定向合成具有所需性能的材料是固体材料化学中一个热门的目标。该项目由美国国家科学基金会材料研究部的固态和材料化学计划资助，开发了通过碱金属卤酸盐和金属卤化物的复分解反应直接合成多元硫化物的方法。它是基于这样的假设：在这些反应中，起始反应物中存在的chalcomallate积木在目标化合物中保持不变。大量含有不同负电荷和共价度的主族元素的合铝单元的可用性使它们成为合成具有理想应用的材料的理想选择。通过选择合适的构建块和金属离子材料的组合，可以产生与磁性相关的有用性能，从而合理地设计离子导电和氧化还原性能。这项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化物晶格。实验合成工作与预测密度泛函理论(DFT)对可能结构和组成的热力学稳定性进行了紧密结合。DFT计算与化学直觉相结合，从组成空间中向下选择最有希望的合成候选者，然后合成这些候选者来验证理论预测。这一合理合成复杂硫化物的协同实验-理论方法可移植到具有广泛应用范围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NSF的法定使命，并通过使用基金会的智力优势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.