Ultrahigh Pressure Crystallographic Passage Toward Metallic Hydrogen

Ultrahigh Pressure Crystallographic Passage Toward Metallic Hydrogen | 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 Physical Sciences - Article Ultrahigh Pressure Crystallographic Passage Toward Metallic Hydrogen Ho-Kwang Mao, Cheng Ji, Bing Li, Jie Luo, Yongsheng Zhao, yuan liu, and 13 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5080559/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 May, 2025 Read the published version in Nature → Version 1 posted You are reading this latest preprint version Abstract Crystallographic evolution of hydrogen under multi-megabar compression is a key problem in condensed-matter physics and unsolved challenge for experimentalists and theoreticians. Although dozens of crystal structures have been proposed by theory, only one, the simple hexagonal-close-packed (hcp) structure, has been previously confirmed in experiments. Utilizing new-generation synchrotron nano-focused X-ray probes developed for micron-sized hydrogen crystals at pressures above 212 GPa, we are able to observe the transition from hcp H2 to a larger hexagonal supercell with lattice parameters expanding to √3✕a and 2✕c of hcp, in which the characteristic hcp peaks (1 0 0), (0 0 2), and (1 0 1) become (1 1 0), (0 0 4), and (1 1 2), respectively, and three new peaks, (1 0 1), (1 0 3), and (2 0 1), of the supercell appear. Theoretical calculations based on our XRD results found a time-averaged structure model in space group P6 ̅2c (190) with alternating layers of spherically disordered H2 molecules and ordered molecules toward a graphene-like atomic H network. Such a hexagonal supercell has not been reported by any previous theoretical study for post-hcp phase, but is close to a number of theoretical models with mixed-layer structures. The clear evidence of a structural transition beyond hcp marks the polymerization nature of molecular-to-atomic hydrogen transition. Physical sciences/Physics/Condensed-matter physics/Phase transitions and critical phenomena Physical sciences/Physics/Condensed-matter physics/Structure of solids and liquids Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SI.docx SI-Ultrahigh Pressure Crystallographic Passage Toward Metallic Hydrogen Cite Share Download PDF Status: Published Journal Publication published 14 May, 2025 Read the published version in Nature → 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-5080559","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":356875912,"identity":"adf655f4-7bc3-44cd-bd76-f5300447b616","order_by":0,"name":"Ho-Kwang 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