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1、PublishedonWeb07/09/2004OxygenGas-InducedLip-LipInteractionsonaDouble-WalledCarbonNanotubeEdgeYongSooChoi,†KyungAhPark,†ChangwookKim,‡andYoungHeeLee*,†ContributionfromtheDepartmentofPhysics,InstituteofBasicScience,CenterforNanotubesandNanostructuredComposites,SungkyunkwanUniVersity
2、,Suwon440-746,Korea,andCAETeam,CorporateR&DCenter,SamsungSDICo.,LTD,Yongin,449-577,KoreaReceivedDecember3,2003;E-mail:leeyoung@skku.eduAbstract:WehaveinvestigatedadsorptionofanO2moleculeonadouble-walledcarbonnanotube(DWCNT)edgeusingdensityfunctionaltheorycalculations.AnO2moleculead
3、sorbsexothermallywithoutanadsorptionbarrieratopennanotubeedgesthatareenergeticallyfavorablewithalargeadsorptionenergyofabout-9eVinmostcases.DissociativeadsorptionofanO2moleculeinducesvariousspontaneouslip-lipinteractionsviathebridgedcarbonatoms,generatingtheclosedtubeends.Thisexpla
4、inswhytheDWCNTsarechemicallymorestablethanthesingle-wallednanotubesduringobservedfieldemissionexperiments.Thefieldemissiontakesplaceviathelocalizedstatesofthebridgedcarbonatoms,notviathoseoftheadsorbedoxygenatomsparticularlyinthearmchairnanotubes.WealsofindthatsomeO2precursorstates
5、existasabridgebetweentubeedges.IntroductionDespitesuchdemandsofintensiveresearchesforoxygenadsorbatesonSWCNTsandDWCNTsfromexperiment,Oxygenmoleculeisoneoftheimportantambientgasesthattheoreticalmodelsarerare.Aselectiveetchingofamorphousplayanessentialroleinmanyaspectsofcarbonnanotub
6、escarbonsfromSWCNTsbyoxygengaseshasbeensuccessfully(CNTs).Thepresenceofoxygengasesonthenanotubewalldescribed.6Unlikestrongchemisorptionofoxygenmoelculesinducesachargetransferfromnanotubetoadsorbate,creating1,2onCNTedges,physisorptionofO2moleculeonthetubewallahole-typechargecarrieri
7、nthenanotube.Theyalsomodifydependsstronglyonthespinstates.11Yet,notheoreticalmodeltheworkfunctionofthemetal-nanotubecontactwhichgoverns3forO2adsorptionontheDWCNTedgeshasbeenreported.thetransportpropertiesofthenanotubetransistors.OxygenMoreover,theadvantageofthismodelforDWCNTscanbeg
8、aseshavebeenalsousedforpur
