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1、VOLUME85,NUMBER8PHYSICALREVIEWLETTERS21AUGUST2000First-PrinciplesStudyofLi-IntercalatedCarbonNanotubeRopesJijunZhao,1,*AlperBuldum,1JieHan,2andJianPingLu1,†1DepartmentofPhysicsandAstronomy,UniversityofNorthCarolinaatChapelHill,ChapelHill,NorthCarolina275992NASAAmesResearchCente
2、r,MailStopT27A-1,MoffettField,California94035(Received11October1999)WestudiedLi-intercalatedcarbonnanotuberopesbyfirst-principlesmethods.ResultsshowchargetransferbetweenLiandCandsmallstructuraldeformationduetointercalation.Boththeinteriorofthenanotubeandtheinterstitialspaceares
3、usceptibleforintercalation.TheLiintercalationpotentialofasingle-wallednanotuberopeiscomparabletothatofgraphiteandalmostindependentoftheLidensityuptoaroundLiC2,asobservedinrecentexperiments.ThisdensityissignificantlyhigherthanthatofLi-intercalatedgraphite,makingthenanoropeapromi
4、singcandidatefortheanodematerialinbatteryapplications.PACSnumbers:71.20.Tx,61.48.+c,68.65.+g,71.15.PdCarbonnanotubesareattractinginterestasconstituentsThetubebundleismodeledbyauniformtwo-ofnovelnanoscalematerialsanddeviceapplicationsdimensionalhexagonallattice.TheSWNTsstudiedhe
5、re[1–3].Novelmechanic,electronic,magnetic[2],andincludeboth(10,0),(12,0)zigzagand(8,8),(10,10)arm-chemicalproperties[3]intheseone-dimensionalma-chairtubes.TheLi-intercalatedgraphiteandbulkLiareterialshavebeendiscovered.Single-wallednanotubesalsoinvestigatedasreferences.Theiniti
6、alconfigurationof(SWNTs)formnanoropebundleswithclose-packedtwo-Liatomsisassumedtobeonhigh-symmetricsiteswhichdimensionaltriangularlattices[4].TheseropecrystallitesmaximizetheLi-Lidistance(seeTableIIfordetails).mightofferanall-carbonhostlatticeforintercalationandFigure1showsther
7、elaxedstructureandchargedensityenergystorage.OnanalogyoftheLiintercalatedgraphiteofthe(10,0)tubebundlewith5Liatomsperunitcell.[5],carbonnanoropeisexpectedtobeacandidateofanodematerialsforLi-ionbatteryapplications[6].RecentexperimentsfoundmuchhigherLicapacity(Li1.6C6)inSWNTsthan
8、thoseofgraphite(LiC6)[7].TheLicapacitycanbefurtherimpr