Observation of a mixed close-packed structure in superionic water

The study of superionic (SI) water has been a highly active research area since its theoretical prediction. Despite significant experimental and computational efforts, its melting curve and the stability of different oxygen lattices remain debated, impacting our understanding of SI ice's peculiar transport properties. Experimental results at lower pressures show disagreement, whereas data at higher pressures are scarce due to the extreme challenges of such experiments. In this work, we present ultrafast X-ray diffraction results of water compressed by multiple shocks to pressures up to ~ 180 GPa. At pressures exceeding 150 GPa and temperatures around 2500 K, our diffraction patterns challenge the pure FCC-SI phase model, providing experimental evidence of the mixed close-packed superionic phase predicted by advanced ab initio calculations. At lower pressures, we observe simultaneous signatures of BCC and FCC structures within a pressure-temperature range consistent with some static-compression experiments, helping to resolve contradictory results in literature. These insights offer new constraints on the stability domains of SI phases and reveal detailed structural features, such as stacking faults. Our results advance the structural understanding of high-pressure SI ice to a level approaching that of ice I polymorphs, with potential implications for water-rich interiors of giant planets.

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Journal
Nature Communications
Published
2025-12-07
DOI
https://doi.org/10.1038/s41467-025-67063-2
Primary Topic
High-pressure geophysics and materials
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article
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article

Observation of a mixed close-packed structure in superionic water

Jan‐Patrick Schwinkendorf, A. Pelka, Frédéric Lefèvre, N. J. Hartley et al.
Nature Communications
High-pressure geophysics and materials
article

Observation of a mixed close-packed structure in superionic water

Jan‐Patrick Schwinkendorf, A. Pelka, Frédéric Lefèvre, N. J. Hartley, L. Lecherbourg, William S. Lynn, Pierre May, M.G. Stevenson, J. Lütgert, A. Benuzzi‐Mounaix, L. B. Fletcher, Jan Vorberger, Minxue Tang, T. Toncian, M. L. Herbert, S. Di Dio Cafiso, Zuzana Konôpková, Alejandro Laso García, Jean‐Alexis Hernandez, Hauke Höppner, Armin Bergermann, Martin French, M. Nakatsutsumi, C. Strohm, A. E. Gleason, B. Heuser, R. Redmer, Thomas R. Preston, Karen Appel, Rachel J. Husband, Adrien Descamps, Zhiyu He, G. Dyer, G. D. Glenn, Lisa Randolph, S. Schumacher, S. H. Glenzer, Eric Galtier, Mungo Frost, Carsten Baehtz, Silvia Pandolfi, Oliver Humphries, K. Voigt, Bob Nagler, T. E. Cowan, D. Kraus, Yoann Guarnelli, Dimitri Khaghani, E. Brambrink, A. Ravasio, Björn Lindqvist, Hae Ja Lee, Mandy Bethkenhagen, Benjamin K. Ofori-Okai, U. Zastrau, L. Andriambariarijaona, Eric Cunningham, Christopher Schoenwaelder, T. Vinci, E. E. McBride, D. S. Bespalov, Chongbing Qu, J. Rips, Jean-Paul Naedler, M. Masruri, D. Ranjan, A. K. Schuster, Jonas Kuhlke
article en

Abstract

The study of superionic (SI) water has been a highly active research area since its theoretical prediction. Despite significant experimental and computational efforts, its melting curve and the stability of different oxygen lattices remain debated, impacting our understanding of SI ice's peculiar transport properties. Experimental results at lower pressures show disagreement, whereas data at higher pressures are scarce due to the extreme challenges of such experiments. In this work, we present ultrafast X-ray diffraction results of water compressed by multiple shocks to pressures up to ~ 180 GPa. At pressures exceeding 150 GPa and temperatures around 2500 K, our diffraction patterns challenge the pure FCC-SI phase model, providing experimental evidence of the mixed close-packed superionic phase predicted by advanced ab initio calculations. At lower pressures, we observe simultaneous signatures of BCC and FCC structures within a pressure-temperature range consistent with some static-compression experiments, helping to resolve contradictory results in literature. These insights offer new constraints on the stability domains of SI phases and reveal detailed structural features, such as stacking faults. Our results advance the structural understanding of high-pressure SI ice to a level approaching that of ice I polymorphs, with potential implications for water-rich interiors of giant planets.

Nature CommunicationsVol. 17(1)
Queen's University Belfast (GB), Centre National de la Recherche Scientifique (FR), École Polytechnique (FR), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Helmholtz-Zentrum Dresden-Rossendorf (DE), Deutsches Elektronen-Synchrotron DESY (DE), SLAC National Accelerator Laboratory (US), European Synchrotron Radiation Facility (FR), Sorbonne Université (FR), Laboratoire pour l'Utilisation des Lasers Intenses (FR), CEA DAM Île-de-France (FR), CEA Paris-Saclay (FR), Institut de minéralogie, de physique des matériaux et de cosmochimie (FR), University of Rostock (DE), European X-Ray Free-Electron Laser (DE), Stanford University (US)
Openalex Percentile: Top 60%
High-pressure geophysics and materials
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