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Phase behaviours of superionic water at planetary conditions

Accepted version
Peer-reviewed

Type

Article

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Authors

Cheng, Bingqing 
Bethkenhagen, Mandy 
Pickard, Christopher  ORCID logo  https://orcid.org/0000-0002-9684-5432
Hamel, Sebastien 

Abstract

Most water in the universe may be superionic, and its thermodynamic and transport properties are crucial for planetary science but difficult to probe experimentally or theoretically. We use machine learning and free energy methods to overcome the limitations of quantum mechanical simulations, and characterize hydrogen diffusion, superionic transitions, and phase behaviors of water at extreme conditions. We predict that a close-packed superionic phase with mixed stacking is stable over a wide temperature and pressure range, while a body-centered cubic phase is only thermodynamically stable in a small window but is kinetically favored. Our phase boundaries, which are consistent with the existing-albeit scarce-experimental observations, help resolve the fractions of insulating ice, different superionic phases, and liquid water inside of ice giants.

Description

Keywords

Journal Title

Nature Physics

Conference Name

Journal ISSN

1745-2473

Volume Title

Publisher

Nature Research

Rights

All rights reserved
Sponsorship
Engineering and Physical Sciences Research Council (EP/P022596/1)