Formation and characterization of iron superhydrides FeHx with x = 6 beyond 230 GPa

This follow-up proposal focuses on the characterization of the nature of phase transitions in FeHx compounds (with x = 6 or higher) beyond 230 GPa, that have yet been only predicted theoretically. It also aims to provide insights in the pressure-induced rearrangements of local electronic and atomic structures in these compounds that remain highly controversial. In our recent experiment (ES-1247), we could successfully reproduce the formation of known FeH/FeH2/FeH3/FeH5 compounds and characterized their local atomic and electronic arrangements from XANES and EXAFS measurements combined with XRD to 230 GPa. At the highest pressure, our data strongly indicate a phase transition potentially to a higher stoichiometry FeHx compound with x = 6. Here, we propose to extend our measurements using our established protocol to explore the formation and local atomic and electronic structure of this new compound. Also, we plan to extend our XAS study of Fe up to the 500 GPa range.

本后续提案聚焦于230吉帕斯卡（GPa）以上FeHx化合物（x≥6）相变本质的表征——这类化合物目前仅停留在理论预测阶段。同时，本提案旨在阐明这些化合物中压力诱导的局域电子与原子结构重排机制，相关研究目前仍存在较大争议。在我们近期的实验（ES-1247）中，我们成功复现了已知FeH/FeH₂/FeH₃/FeH₅化合物的形成过程，并结合X射线衍射（XRD）、X射线吸收近边结构（XANES）与扩展X射线吸收精细结构（EXAFS）测量，表征了它们在230 GPa压力范围内的局域原子与电子排布。在最高压力下，我们的数据强烈暗示存在向更高化学计量比FeHx化合物（x=6）的相变可能性。在此，我们提议沿用已建立的实验方案，拓展测量范围以探究该新型化合物的形成过程及其局域原子与电子结构。此外，我们计划将铁的X射线吸收光谱（XAS）研究拓展至500 GPa压力范围。