Phase diagram of palladium characterized in situ via synchrotron X-ray diffraction coupled with laser-heated diamond anvil cell

Phase diagram of palladium characterized in situ via synchrotron X-ray diffraction coupled with laser-heated diamond anvil cell | 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 Phase diagram of palladium characterized in situ via synchrotron X-ray diffraction coupled with laser-heated diamond anvil cell Simone Anzellini, Samuel Baty, Leonid Burakovsky, Jose Luis Rodrigo-Ramon, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9640501/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 Transition metals exhibit complex structural behavior under extreme conditions, yet their high-pressure–high-temperature phase diagrams remain poorly con- strained experimentally. Palladium exemplifies this problem, with a predicted face-centered cubic (f cc) to body-centered cubic (bcc) transition that has eluded experimental detection. Here we demonstrate that this discrepancy arises from kinetic constraints and can be overcome through melt-mediated pathways. Using in situ synchrotron X-ray diffraction in a laser-heated diamond anvil cell, we map the phase diagram of palladium up to 107 GPa and 6800 K and directly access a bcc polymorph via rapid quenching from the liquid. We show that, although ther- modynamically competitive, the bcc phase is kinetically inaccessible along the solid-state pathway, but becomes stabilized near melting where enhanced atomic mobility enables structural selection. This establishes a general mechanism by which high-pressure phases can remain hidden in experiments despite theoretical stability. Our results reconcile long-standing theory–experiment inconsistencies for palladium and suggest that similar kinetic limitations may govern phase sta- bility across d-band metals. In addition, we determine a high-precision melting curve and thermal equation of state in quantitative agreement with ab initio sim- ulations, providing a benchmark for materials under extreme conditions. These findings redefine the experimental accessibility of high-pressure phases and call for a reassessment of phase diagrams where kinetic effects have been overlooked. Physical sciences/Materials science/Condensed-matter physics Physical sciences/Physics/Condensed-matter physics Melting Extreme Conditions Transition Metals Laser-heating Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SuppMat.pdf Supplementary Material 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. 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-9640501","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":636314413,"identity":"1ba2e3f2-609c-4518-b4b6-1847dd7b7456","order_by":0,"name":"Simone 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Laser-heating","lastPublishedDoi":"10.21203/rs.3.rs-9640501/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9640501/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Transition metals exhibit complex structural behavior under extreme conditions,\r\nyet their high-pressure–high-temperature phase diagrams remain poorly con-\r\nstrained experimentally. Palladium exemplifies this problem, with a predicted\r\nface-centered cubic (f cc) to body-centered cubic (bcc) transition that has eluded\r\nexperimental detection. Here we demonstrate that this discrepancy arises from\r\nkinetic constraints and can be overcome through melt-mediated pathways. Using\r\nin situ synchrotron X-ray diffraction in a laser-heated diamond anvil cell, we map\r\nthe phase diagram of palladium up to 107 GPa and 6800 K and directly access a\r\nbcc polymorph via rapid quenching from the liquid. We show that, although ther-\r\nmodynamically competitive, the bcc phase is kinetically inaccessible along the\r\nsolid-state pathway, but becomes stabilized near melting where enhanced atomic\r\nmobility enables structural selection. This establishes a general mechanism by\r\nwhich high-pressure phases can remain hidden in experiments despite theoretical\r\nstability. Our results reconcile long-standing theory–experiment inconsistencies\r\nfor palladium and suggest that similar kinetic limitations may govern phase sta-\r\nbility across d-band metals. In addition, we determine a high-precision melting curve and thermal equation of state in quantitative agreement with ab initio sim-\r\nulations, providing a benchmark for materials under extreme conditions. These\r\nfindings redefine the experimental accessibility of high-pressure phases and call\r\nfor a reassessment of phase diagrams where kinetic effects have been overlooked.","manuscriptTitle":"Phase diagram of palladium characterized in situ\nvia synchrotron X-ray diffraction coupled with\nlaser-heated diamond anvil cell","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-14 06:07:24","doi":"10.21203/rs.3.rs-9640501/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":"5e4b65b5-a9e7-4fc9-88e4-fffdfd7b9226","owner":[],"postedDate":"May 14th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"This content is not available.","date":"2026-05-13T09:41:43+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewersInvited","content":"4","date":"2026-05-13T09:01:03+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-05-07T15:14:38+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-05-07T12:46:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Nature Communications","date":"2026-05-07T09:42:32+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":67727986,"name":"Physical sciences/Materials science/Condensed-matter physics"},{"id":67727987,"name":"Physical sciences/Physics/Condensed-matter physics"}],"tags":[],"updatedAt":"2026-05-14T06:07:24+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-14 06:07:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9640501","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9640501","identity":"rs-9640501","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}