Quasi-degenerate cation occupation enables nearly defect-free functional crystals

Quasi-degenerate cation occupation enables nearly defect-free functional crystals | 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 Quasi-degenerate cation occupation enables nearly defect-free functional crystals Haohai Yu, Jinfeng Han, Fei Liang, Kui Wu, Deliang Cui, Dazhi Lu, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9624869/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 Chemical substitution is an effective strategy to enhance the desired performances of materials based on known structural prototypes. However, it almost invariably introduces intrinsic defects, such as vacancies and twinning defects, which couple with dopants and obscure or degrade the intrinsic properties. Therefore, chemical substitution that enables atomically precise engineering of materials without generating defect structures remains challenging. Here, we propose a quasi-degenerate cation occupation strategy to overcome this detrimental coupling and successfully apply it to the langasite-family nonlinear optical (NLO) crystal, La 3 TiGa 5 O 14 (LGTi). Therein, the cross-site occupation of Ti and Ti 3+ /Ti 4+ redox flexibility improve the kinetic accessibility of oxygen-vacancy ( V O ) defects associated with cation disorder, enabling their removal during oxidative annealing. The oxidized LGTi single crystal has a V O -related defect concentration below the electron paramagnetic resonance detection limit and exhibits an enhanced NLO performance, including a strong laser damage threshold of 2.53 GW/cm 2 and a large NLO coefficient of 3.51 pm/V, which are the best values ever reported for langasite-family crystals. Overall, this work provides a quasi-degenerate cation occupation strategy to mitigate substitution-induced defects in structurally complex crystalline systems and has great prospects in enhancing material performance. Physical sciences/Materials science/Materials for optics Physical sciences/Materials science/Structural materials Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupportingInformation.docx Supporting Information 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-9624869","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":636801662,"identity":"5d6b6733-2a87-41e2-b250-bbcddad93a55","order_by":0,"name":"Haohai 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Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9624869/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9624869/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eChemical substitution is an effective strategy to enhance the desired performances of materials based on known structural prototypes. However, it almost invariably introduces intrinsic defects, such as vacancies and twinning defects, which couple with dopants and obscure or degrade the intrinsic properties. Therefore, chemical substitution that enables atomically precise engineering of materials without generating defect structures remains challenging. Here, we propose a quasi-degenerate cation occupation strategy to overcome this detrimental coupling and successfully apply it to the langasite-family nonlinear optical (NLO) crystal, La\u003csub\u003e3\u003c/sub\u003eTiGa\u003csub\u003e5\u003c/sub\u003eO\u003csub\u003e14\u003c/sub\u003e (LGTi). Therein, the cross-site occupation of Ti and Ti\u003csup\u003e3+\u003c/sup\u003e/Ti\u003csup\u003e4+\u003c/sup\u003e redox flexibility improve the kinetic accessibility of oxygen-vacancy (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eO\u003c/em\u003e\u003c/sub\u003e) defects associated with cation disorder, enabling their removal during oxidative annealing. The oxidized LGTi single crystal has a \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eO\u003c/em\u003e\u003c/sub\u003e-related defect concentration below the electron paramagnetic resonance detection limit and exhibits an enhanced NLO performance, including a strong laser damage threshold of 2.53 GW/cm\u003csup\u003e2\u003c/sup\u003e and a large NLO coefficient of 3.51 pm/V, which are the best values ever reported for langasite-family crystals. Overall, this work provides a quasi-degenerate cation occupation strategy to mitigate substitution-induced defects in structurally complex crystalline systems and has great prospects in enhancing material performance.\u003c/p\u003e","manuscriptTitle":"Quasi-degenerate cation occupation enables nearly defect-free functional crystals","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-11 10:59:14","doi":"10.21203/rs.3.rs-9624869/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":"1e8e1ee2-06e1-4d11-a424-28b38d1338f7","owner":[],"postedDate":"May 11th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"This content is not available.","date":"2026-05-12T09:04:31+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2026-05-11T00:46:35+00:00","index":3,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2026-05-09T08:22:58+00:00","index":2,"fulltext":"This content is not available."},{"type":"reviewerAgreed","content":"This content is not available.","date":"2026-05-08T13:02:50+00:00","index":1,"fulltext":"This content is not available."},{"type":"reviewersInvited","content":"6","date":"2026-05-08T10:28:52+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-05-06T12:13:31+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-05-06T08:48:56+00:00","index":"","fulltext":""},{"type":"submitted","content":"Nature Communications","date":"2026-05-06T04:45:01+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":67778833,"name":"Physical sciences/Materials science/Materials for optics"},{"id":67778834,"name":"Physical sciences/Materials science/Structural materials"}],"tags":[],"updatedAt":"2026-05-11T10:59:14+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-11 10:59:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9624869","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9624869","identity":"rs-9624869","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}