Evidence for symmetry-reduction in solid H2O above 222 GPa

Evidence for symmetry-reduction in solid H2O above 222 GPa | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Evidence for symmetry-reduction in solid H 2 O above 222 GPa ASHKAN SALAMAT, Zachary Grande, Victor Naden Robinson, Dean Smith, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8428378/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Water (H$_2$O), one of the most consequential compounds in the Solar System, governs the structure and dynamics of icy planets, the terrestrial water cycle, and through the pressure-induced transition from hydrogen to ionic bonding, it exhibits marked changes over the pressure range of planetary interiors. While many materials are expected to favour simple, densely packed lattices with increasing compression, as observed in water ice-X, others %such as the complex hP4 phase of sodium exhibit unexpected structural complexity at extreme pressures. Here we report experimental evidence that water ice undergoes a transformation from ice-X to a less symmetric structure above 222(12) GPa. Synchrotron X-ray diffraction reveals a distortion of the cubic lattice consistent with either \textit{Pbcm} or \textit{P}4$_2$\textit{/nnm} symmetry, the former being strongly favorable by \textit{ab initio} calculations. This transition marks the onset of a new regime of structural complexity in high-pressure H$_2$O, redefining the upper stability limit of ice-X. Physical sciences/Physics/Condensed-matter physics/Phase transitions and critical phenomena Physical sciences/Astronomy and planetary science/Planetary science/Exoplanets Water-ice crystal structure high pressure XRD Full Text Additional Declarations There is NO Competing Interest. Supplementary Files NPSI.pdf Evidence for symmetry-reduction in solid H$_2$O above 222~GPa Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8428378","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":574084808,"identity":"e74d0513-25fe-46b2-b268-c918afb13903","order_by":0,"name":"ASHKAN 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XRD","lastPublishedDoi":"10.21203/rs.3.rs-8428378/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8428378/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Water (H$_2$O), one of the most consequential compounds in the Solar System, governs the structure and dynamics of icy planets, the terrestrial water cycle, and through the pressure-induced transition from hydrogen to ionic bonding, it exhibits marked changes over the pressure range of planetary interiors. \r\nWhile many materials are expected to favour simple, densely packed lattices with increasing compression, as observed in water ice-X, others %such as the complex hP4 phase of sodium \r\nexhibit unexpected structural complexity at extreme pressures. Here we report experimental evidence that water ice undergoes a transformation from ice-X to a less symmetric structure above 222(12) GPa. \r\nSynchrotron X-ray diffraction reveals a distortion of the cubic lattice consistent with either \\textit{Pbcm} or \\textit{P}4$_2$\\textit{/nnm} symmetry, the former being strongly favorable by \\textit{ab initio} calculations. \r\nThis transition marks the onset of a new regime of structural complexity in high-pressure H$_2$O, redefining the upper stability limit of ice-X.","manuscriptTitle":"Evidence for symmetry-reduction in solid H2O above 222 GPa","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-09 07:14:40","doi":"10.21203/rs.3.rs-8428378/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"69da85d9-7656-44d1-9435-3c413aaceb91","owner":[],"postedDate":"February 9th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":62554135,"name":"Physical sciences/Physics/Condensed-matter physics/Phase transitions and critical phenomena"},{"id":62554136,"name":"Physical sciences/Astronomy and planetary science/Planetary science/Exoplanets"}],"tags":[],"updatedAt":"2026-02-09T07:14:40+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-09 07:14:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8428378","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8428378","identity":"rs-8428378","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}