Silica-water superstructure and one-dimensional superionic conduit in Earth's mantle.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37656794.
- Also identified by DOI 10.1126/sciadv.adh3784 and PMC identifier 10854424.
- Licence recorded as CC BY-NC.
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Abstract
Water in Earth's deep interior is predicted to be hydroxyl (OH<sup>-</sup>) stored in nominally anhydrous minerals, profoundly modulating both structure and dynamics of Earth's mantle. Here, we use a high-dimensional neuro-network potential and machine learning algorithm to investigate the weight percent water incorporation in stishovite, a main constituent of the subducted oceanic crust. We found that stishovite and water prefer forming medium- to long-range ordered superstructures, featuring one-dimensional (1D) water channels. Synthesizing single crystals of hydrous stishovite, we verified the ordering of OH<sup>-</sup> groups in the water channels through optical and nuclear magnetic resonance spectroscopy and found an average H-H distance of 2.05(3) Å, confirming simulation results. Upon heating, H atoms were predicted to behave fluid-like inside the channels, leading to an exotic 1D superionic state. Water-bearing stishovite could feature high ionic mobility and strong electrical anisotropy, manifesting as electrical heterogeneity in Earth's mantle.