Ultrafast Yttrium Hydride Chemistry at High Pressures via Non-equilibrium States Induced by an X-ray Free Electron Laser
Emily Siska, G. Alexander Smith, Sergio Villa-Cortes, Lewis J. Conway, Rachel J. Husband, Joshua Van Cleave, Sylvain Petitgirard, Valerio Cerantola, Karen Appel, Carsten Baehtz, V. Bouffetier, Anand Dwivedi, Sebastian Göde, Tais Gorkhover, Zuzana Konôpková, S. M. A. Hosseini‐Saber, Stephan Kuschel, Torsten Laurus, M. Nakatsutsumi, C. Strohm, J. Sztuk-Dambietz, U. Zastrau, D. F. Smith, Keith V. Lawler, Chris J. Pickard, Craig P. Schwartz, Ashkan Salamat
Abstract
Controlling the formation and stoichiometric content of the desired phases of materials has become of central interest for a variety of fields. The possibility of accessing metastable states by initiating reactions by X-ray-triggered mechanisms over ultrashort time scales has been enabled by the development of X-ray free electron lasers (XFELs). Utilizing the exceptionally high-brilliance X-ray pulses from the EuXFEL, we report the synthesis of a previously unobserved yttrium hydride under high pressure, along with nonstoichiometric changes in hydrogen content as probed at a repetition rate of 4.5 MHz using time-resolved X-ray diffraction. Exploiting non-equilibrium pathways, we synthesize and characterize a hydride in a Weaire-Phelan structure type at pressures as low as 125 GPa, predicted using a crystal structure search, with a hydrogen content of 4.0-5.75 hydrogens per cation, that is enthalpically metastable on the convex hull.