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1、PHYSICALREVIEWB80,1741112009Carbonnitride:Abinitioinvestigationofcarbon-richphasesJudyN.Hart,1,*FrederikClaeyssens,2NeilL.Allan,1andPaulW.May11SchoolofChemistry,UniversityofBristol,BristolBS81TS,UnitedKingdom2DepartmentofEngineeringMaterials,SirRobertHadfi
2、eldBuilding,UniversityofSheffield,MappinStreet,SheffieldS13JD,UnitedKingdomReceived28July2009;published17November2009Wehaveexaminedthepotentialenergyhypersurfacesforthecarbon-richphasesofcarbonnitride,CNandC3N,anddiscoveredlow-energystructuresdifferentfromt
3、hosereportedpreviously.Trendsinthepreferredlocalbondingenvironmentshavebeenanalyzedasafunctionofnitrogencontent.Foreachcomposition,severalstructureswithsimilarenergieswerefound,buttheyhaveverydifferentequilibriumvolumes;thestructureproducedduringsynthesiswi
4、llstronglydependonthepreparationconditions.Whenlowdensitiesarefavored,conjugatedplanar-ringstructureswithsp2hybridizedcarbonaremostlikelytobeformed.Thesestructuresaresimilartothosesuggestedaspotentialphotocatalyticmaterials.Athighpressures,thepreferredstruc
5、turescontainthree-coordinatenitrogenandsp3hybridizedcarbon,includingthe-InSstructure,whichwepredicttobethethermodynamicallypreferredstructureforCNunderpositivehydrostaticpressures.Thisstructurehasamoderatelyhighbulkmoduluswithalowerformationenergythan-C3N
6、4andsoshouldbemoreeasilysynthesized.DOI:10.1103/PhysRevB.80.174111PACSnumbers:61.50.Ah,61.66.Fn,62.20.x,71.15.MbI.INTRODUCTIONbeusedasprecursorsforformationofdensecarbonnitridephases,8forexamplebytheapplicationofhighpressure,20Therehasbeenmuchinterestint
7、hesynthesisofcarbonalthoughthishasnotyetbeenachieved.nitrides.-C3N4hasbeenaparticularfocusofsyntheticTheincentiveforstudyofthe-C3N4structurewastheworkduetothepredictionthatitshouldhaveaveryhighwell-knownanalog-SiN,1butithassubsequentlybeen34bulkmodulus
8、430GPa.1Unfortunately,successtodatesuggested21thattheachievablenitrogencontentincarboninthesynthesisofthismaterialhasbeenlimitedtoproduc-nitrideislowerthanforsiliconnitride,duenotonlytothetionofmixtur
