Phase transition kinetics of superionic H2O ice phases revealed by Megahertz X-ray free-electron laser-heating experiments

Journal Article · 22 September 2024 · Nature Communications

DOI: https://doi.org/10.1038/s41467-024-52505-0 · OSTI ID:2447665

Husband, R. J. ; Liermann, H. P. ; McHardy, J. D. ; McWilliams, R. S. ; Goncharov, A. F. ; Prakapenka, V. B. ; Edmund, E. ; Chariton, S.; Konôpková, Z.; Strohm, C.; Sanchez-Valle, C. ; Frost, M. ; Andriambariarijaona, L.; Appel, K. ; Baehtz, C. ; Ball, O. B. ; Briggs, R.; Buchen, J. ; Cerantola, V. ; Choi, J. ; Coleman, A. L. ; Cynn, H. ; Dwivedi, A.; Graafsma, H. ; Hwang, H. ; Koemets, E.; Laurus, T. ; Lee, Y. ; Li, X.; Marquardt, H. ; Mondal, A. ; Nakatsutsumi, M. ; Ninet, S.; Pace, E. ; Pepin, C. ; Prescher, C.; Stern, S.; Sztuk-Dambietz, J.; Zastrau, U. ; McMahon, M. I.

Abstract H ₂ O transforms to two forms of superionic (SI) ice at high pressures and temperatures, which contain highly mobile protons within a solid oxygen sublattice. Yet the stability field of both phases remains debated. Here, we present the results of an ultrafast X-ray heating study utilizing MHz pulse trains produced by the European X-ray Free Electron Laser to create high temperature states of H ₂ O, which were probed using X-ray diffraction during dynamic cooling. We confirm an isostructural transition during heating in the 26-69 GPa range, consistent with the formation of SI-bcc. In contrast to prior work, SI-fcc was observed exclusively above ~50 GPa, despite evidence of melting at lower pressures. The absence of SI-fcc in lower pressure runs is attributed to short heating timescales and the pressure-temperature path induced by the pump-probe heating scheme in which H ₂ O was heated above its melting temperature before the observation of quenched crystalline states, based on the earlier theoretical prediction that SI-bcc nucleates more readily from the fluid than SI-fcc. Our results may have implications for the stability of SI phases in ice-rich planets, for example during dynamic freezing, where the preferential crystallization of SI-bcc may result in distinct physical properties across mantle ice layers.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 2447665
• Journal Information: Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 15; ISSN 2041-1723
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English