Abstract
Silica, water, and hydrogen are known to be the major components of celestial bodies, and have significant influence on the formation and evolution of giant planets, such as Uranus and Neptune. Thus, it is of fundamental importance to investigate their states and possible reactions under the planetary conditions. Here, using advanced crystal structure searches and first-principles calculations in the system, we find that a silica-water compound and a silica-hydrogen compound can exist under high pressures above 450 and 650 GPa, respectively. Further simulations reveal that, at high pressure and high temperature conditions corresponding to the interiors of Uranus and Neptune, these compounds exhibit superionic behavior, in which protons diffuse freely like liquid while the silicon and oxygen framework is fixed as solid. Therefore, these superionic silica-water and silica-hydrogen compounds could be regarded as important components of the deep mantle or core of giants, which also provides an alternative origin for their anomalous magnetic fields. These unexpected physical and chemical properties of the most common natural materials at high pressure offer key clues to understand some abstruse issues including demixing and erosion of the core in giant planets, and shed light on building reliable models for solar giants and exoplanets.
- Received 24 June 2021
- Revised 3 December 2021
- Accepted 24 December 2021
DOI:https://doi.org/10.1103/PhysRevLett.128.035702
© 2022 American Physical Society
Physics Subject Headings (PhySH)
Focus
Mineral Candidates for Planet Interiors
Published 21 January 2022
Computer simulations uncover new high-pressure minerals that may explain the origin of Earth’s water and of Uranus’ and Neptune’s magnetic fields.
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