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.