{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T15:51:27Z","timestamp":1789487487555,"version":"build-2803163510"},"reference-count":42,"publisher":"American Chemical Society (ACS)","issue":"36","license":[{"start":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T00:00:00Z","timestamp":1787788800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-029"},{"start":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T00:00:00Z","timestamp":1787788800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-037"},{"start":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T00:00:00Z","timestamp":1787788800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-045"}],"funder":[{"DOI":"10.13039\/501100004543","name":"China Scholarship Council","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100004543","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,15]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Due to the interesting properties of copper oxides, in particular for catalytic applications, ultrathin oxide layers formed by Cu oxidation have attracted sustained interest. Experimental observations of several surface phases, including the so-called \u201c5\u20137\u201d, \u201c8\u201d, \u201c29\u201d and \u201c44\u201d structures, have sparked ongoing debate. However, their precise atomic configurations remain incompletely resolved. Among these, the \u201c8\u201d phase is particularly challenging, as existing structural models rely on limited experimental evidence. Here, we combine surface X-ray diffraction, direct fitting of experimental data, and density functional theory (DFT) calculations, to determine both the composition and atomic structure of this phase. The resolved structure reveals a dense, interwoven network of four-membered Cu\u2013O rings, comprising two distinct Cu cation species with markedly different structural and electronic characteristics. DFT results show that a substantial electron transfer from the Cu(111) substrate stabilizes its relatively oxygen-rich composition, Cu5O4. This \u201c8\u201d phase is energetically more stable than the most recent Cu8O4 model [Kim, H. J. et al. ACS Nano\u00a02024, 18, 4559\u20134569] across the full range of oxygen chemical potential and is structurally and electronically distinct from the \u201c29\u201d and \u201c44\u201d surface oxides. Its bonding motifs and charge distribution resemble those of Pd5O4 and Ag5O4, formed on oxidized (111) surfaces of palladium and silver, but its formation requires less oxygen-rich conditions, reflecting the stronger affinity of Cu for oxygen.<\/jats:p>","DOI":"10.1021\/acsnano.6c11362","type":"journal-article","created":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T19:51:01Z","timestamp":1788292261000},"page":"25069-25077","source":"Crossref","is-referenced-by-count":0,"title":["Solving the Long-Standing\nCu(111) \u201c8\u201d\nSurface Oxide Puzzle"],"prefix":"10.1021","volume":"20","author":[{"given":"Romain","family":"Bernard","sequence":"first","affiliation":[{"name":"Sorbonne Universite\u0301, Centre National de la Recherche Scientifique, Institut des NanoSciences de Paris, INSP , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jacek","family":"Goniakowski","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301, Centre National de la Recherche Scientifique, Institut des NanoSciences de Paris, INSP , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8665-9695","authenticated-orcid":true,"given":"Claudine","family":"Noguera","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301, Centre National de la Recherche Scientifique, Institut des NanoSciences de Paris, INSP , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alessandro","family":"Coati","sequence":"additional","affiliation":[{"name":"Synchrotron SOLEIL , , ,","place":["Gif-Sur-Yvette Cedex, France, BP 48 91192"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yves","family":"Garreau","sequence":"additional","affiliation":[{"name":"Synchrotron SOLEIL , , ,","place":["Gif-Sur-Yvette Cedex, France, BP 48 91192"]},{"name":"Universite\u0301 Paris Cite\u0301, CNRS , , ,","place":["Paris, France, F-75013"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guilhem","family":"Simon","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301, CNRS , , ,","place":["Paris, France, F75252"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Axel","family":"Wilson","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301, CNRS , , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lei","family":"Zhang","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301 , , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ahmed","family":"Naitabdi","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301 , , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Geoffroy","family":"Pre\u0301vot","sequence":"additional","affiliation":[{"name":"Sorbonne Universite\u0301, Centre National de la Recherche Scientifique, Institut des NanoSciences de Paris, INSP , ,","place":["Paris, France, F-75005"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,8,27]]},"reference":[{"key":"2026091510111074800_cit1","doi-asserted-by":"publisher","first-page":"567","DOI":"10.1006\/jcat.1994.1173","article-title":"Carbon Monoxide Oxidation over Three Different Oxidation\nStates of Copper: Metallic Copper, Copper (I) Oxide, and Copper (II)\nOxide - A Surface Science and Kinetic Study","volume":"147","author":"Jernigan","year":"1994","journal-title":"J. Catal."},{"key":"2026091510111074800_cit2","doi-asserted-by":"publisher","first-page":"2814","DOI":"10.1021\/cs502128q","article-title":"Selective Electrochemical Reduction of Carbon Dioxide\nto Ethylene and Ethanol on Copper(I) Oxide Catalysts","volume":"5","author":"Ren","year":"2015","journal-title":"ACS Catal."},{"key":"2026091510111074800_cit3","doi-asserted-by":"publisher","first-page":"4239","DOI":"10.1021\/acscatal.4c06825","article-title":"Water\u2013Gas Shift Reaction over CuxO\/Cu(111) (x &lt; 2) from a DFT-MKM-kMC\nStudy","volume":"15","author":"Huang","year":"2025","journal-title":"ACS Catal."},{"key":"2026091510111074800_cit4","doi-asserted-by":"publisher","first-page":"3992","DOI":"10.1021\/cr050198b","article-title":"Methanol\nSteam Reforming for Hydrogen\nProduction","volume":"107","author":"Palo","year":"2007","journal-title":"Chem. Rev."},{"key":"2026091510111074800_cit5","doi-asserted-by":"publisher","DOI":"10.1016\/j.susc.2024.122622","article-title":"The Surface\nChemistry of Cuprous Oxide","volume":"751","author":"Hu","year":"2025","journal-title":"Surf. Sci."},{"key":"2026091510111074800_cit6","doi-asserted-by":"publisher","first-page":"1677","DOI":"10.1007\/s12274-020-2791-z","article-title":"Crystal-Plane-Dependent\nRedox Reaction on Cu Surfaces","volume":"13","author":"Li","year":"2020","journal-title":"Nano Res."},{"key":"2026091510111074800_cit7","doi-asserted-by":"publisher","first-page":"424","DOI":"10.1016\/j.surfrep.2015.07.001","article-title":"Atomistic\nDetails of Oxide Surfaces and Surface Oxidation:\nThe Example of Copper and Its Oxides","volume":"70","author":"Gattinoni","year":"2015","journal-title":"Surf.\nSci. Rep."},{"key":"2026091510111074800_cit8","doi-asserted-by":"publisher","DOI":"10.1016\/j.surfrep.2024.100622","article-title":"A Surface Science View onto Cuprous\nOxide: Growth, Termination, Electronic Structure and Optical Response","volume":"79","author":"Nilius","year":"2024","journal-title":"Surf. Sci. Rep."},{"key":"2026091510111074800_cit9","doi-asserted-by":"crossref","unstructured":"Jensen, F.; Besenbacher, F.; Stensgaard, I.\n          Two New Oxygen\nInduced Reconstructions on Cu(111).  Surf.\nSci.1992, 269\/270, 400\u2212404.","DOI":"10.1016\/0039-6028(92)91282-G"},{"key":"2026091510111074800_cit10","doi-asserted-by":"publisher","DOI":"10.1016\/j.apsusc.2021.150148","article-title":"Completing the Picture\nof Initial Oxidation on Copper","volume":"562","author":"Lee","year":"2021","journal-title":"Appl. Surf.\nSci."},{"key":"2026091510111074800_cit11","doi-asserted-by":"publisher","first-page":"15887","DOI":"10.1021\/jacs.4c02424","article-title":"Vacancy Ordering in\nUltrathin Copper Oxide Films on Cu(111)","volume":"146","author":"Zhu","year":"2024","journal-title":"J.\nAm. Chem. Soc."},{"key":"2026091510111074800_cit12","doi-asserted-by":"publisher","first-page":"643","DOI":"10.1016\/0039-6028(86)91065-4","article-title":"The Interaction of Oxygen with Cu(111):\nAdsorption, Incorporation and Reconstruction","volume":"171","author":"Judd","year":"1986","journal-title":"Surf. Sci."},{"key":"2026091510111074800_cit13","doi-asserted-by":"publisher","first-page":"8662","DOI":"10.1021\/jp800713u","article-title":"Reconstruction\nof Cu(111) Induced by a Hyperthermal Oxygen Molecular Beam","volume":"112","author":"Moritani","year":"2008","journal-title":"J. Phys. Chem. C"},{"key":"2026091510111074800_cit14","doi-asserted-by":"publisher","first-page":"26735","DOI":"10.1039\/C4CP04473H","article-title":"Re-Visiting the O\/Cu(111)\nSystem \u2013 When Metastable Surface Oxides Could Become an Issue!","volume":"16","author":"Richter","year":"2014","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026091510111074800_cit15","doi-asserted-by":"publisher","first-page":"26814","DOI":"10.1021\/acsomega.1c04663","article-title":"Revisit of\nXPS Studies of Supersonic O2 Molecular Adsorption on Cu(111):\nCopper Oxides","volume":"6","author":"Hayashida","year":"2021","journal-title":"ACS Omega"},{"key":"2026091510111074800_cit16","doi-asserted-by":"publisher","first-page":"4559","DOI":"10.1021\/acsnano.3c12249","article-title":"Recalibrating the Experimentally\nDerived Structure of the Metastable Surface Oxide on Copper via Machine\nLearning-Accelerated In Silico Global Optimization","volume":"18","author":"Kim","year":"2024","journal-title":"ACS Nano"},{"key":"2026091510111074800_cit17","doi-asserted-by":"publisher","first-page":"105","DOI":"10.1016\/0167-5729(89)90002-2","article-title":"Surface Structure\nDetermination by X-Ray Diffraction","volume":"10","author":"Feidenhans\u2019l","year":"1989","journal-title":"Surf. Sci.\nRep."},{"key":"2026091510111074800_cit18","doi-asserted-by":"publisher","first-page":"5","DOI":"10.1016\/S0167-5729(98)00005-3","article-title":"Oxide Surfaces\nand Metal\/Oxide Interfaces Studied by Grazing Incidence X-Ray Scattering","volume":"32","author":"Renaud","year":"1998","journal-title":"Surf. Sci. Rep."},{"key":"2026091510111074800_cit19","doi-asserted-by":"publisher","first-page":"6729","DOI":"10.1039\/C5CP06933E","article-title":"Incorrect\nDFT-GGA Predictions of the Stability of Non-Stoichiometric\/Polar Dielectric\nSurfaces: The Case of Cu2O(111)","volume":"18","author":"Nilius","year":"2016","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026091510111074800_cit20","doi-asserted-by":"publisher","first-page":"26937","DOI":"10.1021\/acs.jpcc.0c09330","article-title":"Nanopyramidal Reconstruction\nof Cu2O(111): A Long-Standing Surface Puzzle Solved by\nSTM and DFT","volume":"124","author":"Gloystein","year":"2020","journal-title":"J. Phys. Chem. C"},{"key":"2026091510111074800_cit21","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevB.80.075424","article-title":"Experimental\nand Theoretical Study\nof Oxygen Adsorption Structures on Ag(111)","volume":"80","author":"Schnadt","year":"2009","journal-title":"Phys. Rev. B"},{"key":"2026091510111074800_cit22","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevB.102.075427","article-title":"Atomistic Structure Learning Algorithm with Surrogate\nEnergy Model Relaxation","volume":"102","author":"Mortensen","year":"2020","journal-title":"Phys. Rev. B"},{"key":"2026091510111074800_cit23","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevLett.88.246103","article-title":"Two-Dimensional\nOxide on Pd(111)","volume":"88","author":"Lundgren","year":"2002","journal-title":"Phys. Rev.\nLett."},{"key":"2026091510111074800_cit24","doi-asserted-by":"publisher","DOI":"10.1063\/5.0216426","article-title":"Ellingham Diagrams\nof Binary Oxides","volume":"12","author":"Shang","year":"2024","journal-title":"APL Mater."},{"key":"2026091510111074800_cit25","doi-asserted-by":"publisher","first-page":"1654","DOI":"10.1038\/s41563-024-02002-y","article-title":"Two-Dimensional Crystalline Platinum Oxide","volume":"23","author":"Cai","year":"2024","journal-title":"Nat. Mater."},{"key":"2026091510111074800_cit26","doi-asserted-by":"publisher","first-page":"P12018","DOI":"10.1088\/1748-0221\/11\/12\/P12018","article-title":"Real-Time\nControl of\nthe Beam Attenuation with XPAD Hybrid Pixel Detector","volume":"11","author":"Dawiec","year":"2016","journal-title":"J. Instrum."},{"key":"2026091510111074800_cit27","doi-asserted-by":"publisher","first-page":"1324","DOI":"10.1107\/S1600576715009607","article-title":"BINoculars: Data Reduction and Analysis Software for Two-Dimensional Detectors\nin Surface X-Ray Diffraction","volume":"48","author":"Roobol","year":"2015","journal-title":"J. Appl. Crystallogr."},{"key":"2026091510111074800_cit28","doi-asserted-by":"publisher","first-page":"15687","DOI":"10.1021\/acsnano.3c02821","article-title":"The Ground State of Epitaxial Germanene on Ag(111)","volume":"17","author":"Zhang","year":"2023","journal-title":"ACS Nano"},{"key":"2026091510111074800_cit29","volume-title":"International Tables\nfor Crystallography","author":"Prince","year":"2004","edition":"3"},{"key":"2026091510111074800_cit30","doi-asserted-by":"publisher","first-page":"222","DOI":"10.1016\/0022-3093(95)00355-X","article-title":"Ab Initio\nMolecular Dynamics for Liquid Metals","volume":"192\u2013193","author":"Kresse","year":"1995","journal-title":"J. Non-Cryst.\nSolids"},{"key":"2026091510111074800_cit31","doi-asserted-by":"publisher","first-page":"15","DOI":"10.1016\/0927-0256(96)00008-0","article-title":"Efficiency of Ab-Initio Total Energy\nCalculations for\nMetals and Semiconductors Using a Plane-Wave Basis Set","volume":"6","author":"Kresse","year":"1996","journal-title":"Comput. Mater. Sci."},{"key":"2026091510111074800_cit32","doi-asserted-by":"publisher","first-page":"17953","DOI":"10.1103\/PhysRevB.50.17953","article-title":"Projector\nAugmented-Wave Method","volume":"50","author":"Blo\u0308chl","year":"1994","journal-title":"Phys. Rev. B"},{"key":"2026091510111074800_cit33","doi-asserted-by":"publisher","first-page":"1758","DOI":"10.1103\/PhysRevB.59.1758","article-title":"From Ultrasoft Pseudopotentials\nto the Projector Augmented-Wave\nMethod","volume":"59","author":"Kresse","year":"1999","journal-title":"Phys. Rev. B"},{"key":"2026091510111074800_cit34","doi-asserted-by":"publisher","first-page":"13244","DOI":"10.1103\/PhysRevB.45.13244","article-title":"Accurate and Simple\nAnalytic Representation of the Electron-Gas Correlation\nEnergy","volume":"45","author":"Perdew","year":"1992","journal-title":"Phys. Rev. B"},{"key":"2026091510111074800_cit35","doi-asserted-by":"publisher","first-page":"3865","DOI":"10.1103\/PhysRevLett.77.3865","article-title":"Generalized\nGradient Approximation\nMade Simple","volume":"77","author":"Perdew","year":"1996","journal-title":"Phys. Rev. Lett."},{"key":"2026091510111074800_cit36","doi-asserted-by":"publisher","DOI":"10.1103\/PhysRevLett.100.136406","article-title":"Restoring the Density-Gradient\nExpansion for Exchange in Solids and Surfaces","volume":"100","author":"Perdew","year":"2008","journal-title":"Phys. Rev. Lett."},{"key":"2026091510111074800_cit37","doi-asserted-by":"publisher","first-page":"8207","DOI":"10.1063\/1.1564060","article-title":"Hybrid Functionals\nBased on a Screened\nCoulomb Potential","volume":"118","author":"Heyd","year":"2003","journal-title":"J. Chem. Phys."},{"key":"2026091510111074800_cit38","doi-asserted-by":"publisher","first-page":"5636","DOI":"10.1039\/C7CP08387D","article-title":"Temperature-Dependent\nPhase Evolution of Copper-Oxide\nThin-Films on Au(111)","volume":"20","author":"Mo\u0308ller","year":"2018","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026091510111074800_cit39","doi-asserted-by":"publisher","DOI":"10.1088\/1361-648X\/ac2534","article-title":"Termination-Dependent\nElectronic Structure and Atomic-Scale Screening Behavior of the Cu2O(111) Surface","volume":"33","author":"Gloystein","year":"2021","journal-title":"J. Phys.: Condens. Matter"},{"key":"2026091510111074800_cit40","doi-asserted-by":"publisher","first-page":"893","DOI":"10.1021\/cr00005a013","article-title":"A Quantum\nTheory of Molecular Structure and Its Applications","volume":"91","author":"Bader","year":"1991","journal-title":"Chem. Rev."},{"key":"2026091510111074800_cit41","doi-asserted-by":"publisher","first-page":"354","DOI":"10.1016\/j.commatsci.2005.04.010","article-title":"A Fast and Robust Algorithm for Bader\nDecomposition of Charge Density","volume":"36","author":"Henkelman","year":"2006","journal-title":"Comput. Mater.\nSci."},{"key":"2026091510111074800_cit42","doi-asserted-by":"publisher","first-page":"1272","DOI":"10.1107\/S0021889811038970","article-title":"VESTA 3 for Three-Dimensional Visualization of Crystal, Volumetric\nand Morphology Data","volume":"44","author":"Momma","year":"2011","journal-title":"J. Appl. Crystallogr."}],"container-title":["ACS Nano"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acsnano.6c11362","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/ancac3\/article-pdf\/20\/36\/25069\/67513192\/acsnano.6c11362.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/ancac3\/article-pdf\/20\/36\/25069\/67513192\/acsnano.6c11362.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T14:34:52Z","timestamp":1789482892000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/ancac3\/article\/20\/36\/25069\/5339470\/Solving-the-Long-Standing-Cu-111-8-Surface-Oxide"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,27]]},"references-count":42,"journal-issue":{"issue":"36","published-online":{"date-parts":[[2026,8,27]]},"published-print":{"date-parts":[[2026,9,15]]}},"URL":"https:\/\/doi.org\/10.1021\/acsnano.6c11362","relation":{},"ISSN":["1936-0851","1936-086X"],"issn-type":[{"value":"1936-0851","type":"print"},{"value":"1936-086X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,27]]}}}