CAREER: Chemical Frustration - A Guiding Principle for the Discovery and Interpretation of New Complex Intermetallic Phases

技术概要：合成和结构研究不断揭示金属间相是一个无与伦比的结构复杂性和多样性的领域。 这种多样性的扩展速度远远超过了能够解释和预测这种结构化学的理论模型的发展速度。 这种模型的缺乏是设计具有定制结构的新金属间化合物和合金材料的瓶颈。 一个共同的主题可以看出，在最近的理论和实验研究的结果复杂的金属间相，可以作为一个更全面的理论框架的基础。 这些相的结构复杂性通常可以追溯到相互排斥的键合或几何堆积模式之间的竞争或共存，通过与磁挫折现象的类比，这里称为“化学挫折”的张力。 在SSMC/DMR计划的支持下，该项目旨在通过检查旨在包含简单密堆积（SCP）和四面体堆积（TCP）变体之间的固有张力的金属间化合物系统来开发这一概念。 金属间化合物系统将研究与固态合成，旨在发现新的阶段，这些新阶段的结构分析，和电子结构计算。 理论上的努力将包括为检测和分析竞争化学键合类型而设计的理论工具的开发。 这些理论工具将基于应用于Hückel计算的矩量法，并根据密度泛函理论（DFT）结果进行校准。 与此同时，还将实施一项教育计划，包括创建固态化学网络资源库，作为国家科学数字图书馆的一部分，以及为该图书馆开发材料。非技术性总结：金属间化合物相形成了对材料科学极其重要的化合物大家族。 它们采用了各种各样的晶体结构，这些结构还没有用化学键的概念来解释。 缺乏理解和预测这些相的优选晶体结构的理论框架是设计具有用于储氢、催化和超导性的有用性质的新金属材料的限制因素。 在这个SSMC/DMR支持的项目中，采用联合理论和实验方法来理解这些相的晶体结构背后的驱动力，并对这些结构进行一定程度的控制。 该方法得出了一个共同的主题，已被认为在一些最复杂的金属间化合物晶体结构：结构的复杂性可以链接到相互排斥的键合类型之间的张力共存于同一阶段。 在这个项目中，将通过选择在优选的化学键合和原子堆积类型中具有内在冲突的元素组合来诱导这种张力，从而寻找新的化合物。 这种设计新金属间化合物结构的方法具有促进用于广泛应用的新合金的开发的潜力。 几种待研究的化合物也被认为具有储氢和超导的有用材料特性。 这项工作的教育和社会影响也将是相当大的：该项目将包括创建固态化学网络资源库，为化学教师和有兴趣在课堂上包括材料科学当前主题的教师提供教育材料。 该项目将通过代表性不足群体成员的参与促进科学的多样性。

TECHNICAL SUMMARY: Synthetic and structural studies are continuously revealing intermetallic phases to be a domain of unparalleled structural complexity and diversity. The rate at which this diversity is expanding far exceeds that of the development of theoretical models capable of accounting for and making predictions regarding this structural chemistry. The absence of such models is a bottleneck in the design of new intermetallic and alloy materials with tailored structures. A common theme can be perceived in the results of recent theoretical and experimental studies on complex intermetallic phases that may serve as the basis for a more comprehensive theoretical framework. Structural complexity in these phases can often be traced to a competition between or coexistence of mutually exclusive bonding or geometrical packing modes, a tension referred to here as "chemical frustration", by analogy with the phenomenon of magnetic frustration. Under the support of the SSMC/DMR program, this project aims to develop this concept through the examination of intermetallic systems designed to contain inherent tensions between variants on simple close-packing (SCP) and tetrahedra-based packing (TCP). Intermetallic systems will be studied with solid state synthesis aimed at the discovery of new phases, the structural analysis of these new phases, and electronic structure calculations. The theoretical efforts will include the development of theoretical tools designed for the detection and analysis of competing chemical bonding types. These theoretical tools will be based on the Moments Method applied to Hückel calculations calibrated against Density Functional Theory (DFT) results. In parallel, an education plan will be pursued involving the creation of the Solid State Chemistry Web Resource Library as part of the National Science Digital Library, as well as the development of materials for this library.NON-TECHNICAL SUMMARY: Intermetallic phases form a broad family of compounds of immense importance to materials science. They adopt a diverse array of crystal structures that has yet to be accounted for with chemical bonding concepts. The absence of a theoretical framework for understanding and predicting the preferred crystal structures of these phases is a limiting factor in the design of new metallic materials with useful properties for hydrogen storage, catalysis, and superconductivity. In this SSMC/DMR-supported project, a joint theoretical and experiment approach is taken to develop understanding the driving forces underlying the crystal structures of these phases, and to gain some degree of control over these structures. The approach draws a common theme that has been perceived in some of the most complex intermetallic crystal structures: structural complexity can be linked to a tension between mutually exclusive bonding types coexisting in the same phase. In this project, new compounds will be sought out by inducing such tension through the selection of combinations of elements with inherent conflicts in the preferred types of chemical bonding and atomic packing. This approach to the design of new intermetallic structures has the potential of facilitating the development of new alloys for a wide range of applications. Several of the compounds to be investigated are also anticipated to have useful materials properties for hydrogen storage and superconductivity. The educational and social impacts of this work will also be considerable: the project will include the creation of the Solid State Chemistry Web Resource Library, a repository of educational materials for chemistry teachers and instructors interested in including current topics in materials science in their classes. The project will promote diversity in science through the participation of members of underrepresented groups.