Superionic-like Diffusion in Yttrium Dihydride

Superionic-like Diffusion in Yttrium Dihydride | 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 Superionic-like Diffusion in Yttrium Dihydride Yuqing Huang, Jianguo Yu, M. Nedim Cinbiz, Jacob Eapen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5695082/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 May, 2025 Read the published version in Scientific Reports → Version 1 posted 8 You are reading this latest preprint version Abstract For the next-generation high temperature microreactors, yttrium dihydride (YH2) is an attractive solid state neutron moderator. Despite a number of recent investigations, the mechanism of hydrogen transport remains poorly understood. Experimental evaluations of diffusivity are inconclusive with large variations in diffusivities and activation energies. In this work, we perform ab initio molecular dynamics (AIMD) simulations on YH2 for temperatures spanning 300 K to 1200 K. Our main finding is that YH2 shows a superionic-like behavior with hydrogen atoms hopping from one native site to another above a characteristic temperature of 800 K. This correlated motion results in quasi-one-dimensional string-like displacements that enable the hydrogen atoms to diffuse rapidly. We confirm that the octahedral sites are mostly unoccupied, although channeling through them is the most favored pathway between lattice hops above 800 K. At the highest temperature of 1200 K, the string relaxation time is merely of the order of a few picoseconds, which indicates a liquid-like diffusive behavior. Based on the formation of spontaneous thermal vacancies, an order-disorder crossover temperature Tα ~ 800 K is established for YH2 with an activation energy of 0.83 eV for hydrogen diffusion in the superionic-like state. Physical sciences/Materials science/Condensed matter physics Physical sciences/Materials science/Structural materials Physical sciences/Physics/Applied physics Full Text Additional Declarations No competing interests reported. Supplementary Files SupplMaterialSuperionicYH2AIMD.docx Cite Share Download PDF Status: Published Journal Publication published 25 May, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Accepted 13 May, 2025 Reviews received at journal 29 Apr, 2025 Reviews received at journal 28 Apr, 2025 Reviewers agreed at journal 18 Apr, 2025 Reviewers agreed at journal 18 Apr, 2025 Reviewers invited by journal 18 Apr, 2025 Submission checks completed at journal 15 Apr, 2025 First submitted to journal 03 Apr, 2025 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. 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