MRI: Acquisition of an Energy-tunable X-ray Analytical Characterization Tool (EXACT) for Measuring Local Structure and Chemistry in Materials

这项重大研究仪器（MRI）计划资助支持收购基于实验室的能量可调X射线分析表征工具（EXACT），该工具将为散装材料提供特定元素的化学状态和局部原子环境信息。这种仪器还将为同步加速器材料表征方法的新生和未来用户提供一个动手培训平台，使他们能够收集初始数据，为在同步加速器设施进行更先进的测量做准备。该项目还将通过为一个在级别、性别、种族和学科方面高度多样化的团队提供领导机会，产生更广泛的影响。EXACT项目将汇集来自不同区域机构的用户联盟，包括研究型大学，主要是本科院校和历史上的黑人学院和大学。该仪器将作为一个平台，对学者进行辐射-物质相互作用方面的深入培训，并将很好地融入格鲁吉亚理工学院研究生和本科生课程的现有实验室模块。该仪器将作为世界级同步加速器设备的新用户和熟练用户的区域培训中心。能量可调谐性和高能量分辨率探测将增强GT的内部研究能力。使用两种类型的光谱进行测量，以前GT无法使用，现在可以使用EXACT：X射线吸收精细结构（XAFS）和高分辨率X射线发射光谱（XES）。总的来说，XAFS和XES可用于阐明局部原子结构信息，如键距、配位、有序/无序参数、局部对称性和局部化学信息，如氧化态、配体类型等。EXACT设施将提供2-12 keV的X射线能量范围，平均能量分辨率约为1 eV，与标准同步加速器光束线的能量分辨率相当。虽然相对于同步加速器，源通量有一个折衷，但EXACT测量可以在合理的时间尺度上提供有用的XAFS/XES数据（对于浓缩样品，在大约一小时或更短的时间内）。待探索的科学空间包括：电池和燃料电池中活性材料在原位/操作条件下的反应机理;配位化学和电子结构对大块材料性质和f元素材料分离过程的作用;过渡金属、镧系元素和锕系元素络合物中的金属-配体键共价性;用于量子计算的候选自旋液体材料的详细表征和结构筛选;阐明与微生物影响的矿物形成/转化有关的反应机制（例如生物矿化和生物风化）;将催化剂纳米颗粒嵌入金属有机框架中并研究光催化和电催化固氮的机械过程（还原和氧化）在铁和钛基氧化物上与过渡金属基共-氧化物反应，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。

This Major Research Instrumentation (MRI) Program grant supports the acquisition of a lab-based energy-tunable x-ray analytical characterization tool (EXACT), which will provide element-specific chemical-state and local atomic environment information for bulk materials. Such an instrument will also provide a platform for hands-on training of nascent and future users of synchrotron-enabled materials characterization methods by allowing them to gather initial data in preparation for more advanced measurements at synchrotron facilities. The project will also have significant broader impact by providing leadership opportunities to a highly diverse team in terms of rank, gender, race and academic disciplines. The EXACT project will bring together a coalition of users from diverse regional institutions, including research universities, predominantly undergraduate institutions, and historically black colleges and universities. The instrument will serve as a platform for in-depth scholar training on radiation-matter interactions and will merge well into existing laboratory modules of the graduate and the undergraduate curriculum at the Georgia Institute of Technology (GT). The instrument will feature in a regional training hub for new and proficient users of world-class synchrotron facilities.Energy-tunability and high energy resolution detection will enhance in-house research capability at GT. Measurements using two types of spectroscopies, previously unavailable at GT, will now be possible with EXACT: x-ray absorption fine structure (XAFS) and high-resolution x-ray emission spectroscopy (XES). Collectively, XAFS and XES can be used to elucidate local atomic structural information, such as, bond distance, coordination, order/disorder parameter, local symmetry, and local chemical information, such as oxidation state, ligand type, etc. The EXACT facility will provide an x-ray energy range of 2-12 keV with an average energy resolution of about 1 eV, comparable to those at standard synchrotron beamlines. While there is a compromise on the source flux relative to a synchrotron, EXACT measurements can deliver useful XAFS/XES data over a reasonable timescale (within about an hour or even less for concentrated samples). The science space to be explored includes: reaction mechanisms of active materials in batteries and fuel cells under in-situ/operando conditions; role of coordination chemistry and electronic structure on bulk material properties and separations processes of f-element materials; metal-ligand bond covalency in transition metal, lanthanide, and actinide complexes; detailed characterization and structural screening of candidate spin-liquid materials for quantum computing; elucidating reaction mechanisms related to microbially impacted mineral formation/transformation (e.g. biomineralization and bioweathering); mechanistic processes of embedding catalyst nanoparticles in metal organic frameworks and investigating photo and electrocatalytic nitrogen fixation (reduction and oxidation) on iron and titanium based oxides with transition metal based co-catalyst.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.