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1、PHYSICALREVIEWBVOLUME61,NUMBER91MARCH2000-IStructuralphasetransitionincarbonnanotubebundlesunderpressureM.J.PetersDepartmentofPhysicsandAstronomy,AppalachianStateUniversity,Boone,NorthCarolina28608L.E.McNeil,JianPingLu,andDanielKahnDepartmentofPhysicsandAstronomy,Universit
2、yofNorthCarolinaatChapelHill,ChapelHill,NorthCarolina27599~Received22July1999!TheRamanshiftsasfunctionsofpressureweremeasuredfortheradialbreathingmodeandtangentialmodesincarbonnanoropescontaining~10,10!and~17,0!single-walledtubes.AnabruptdecreaseintherateofchangeoftheRaman
3、shiftwithpressureforthetangentialmodes,andthedisappearanceoftheradialbreathingmode,wereobservedatapproximately1.7GPa.ThesechangesintheRamanspectrumresultfromastructuralphasetransitionasthenanoropesarecompressed.Theoreticalcalculationsusingtheempiricalforcemethodcon®rmthist
4、ransition,asindicatedbyacalculateddiscontinuityinthelatticeconstantsandunitcellvolumeat1.7GPa.INTRODUCTIONTheRamanspectraweremeasuredusingamicro-RamanilluminatorattachedtoaDilorXYtriplespectrometer.TheWhilesingle-walledcarbonnanotubes~SWNTs!were12±5lasersourceusedwasaSpect
5、raPhysics2017argonionlaserdiscoveredrelativelyrecently,theirelectronicand6±10settothe5145Ålinewithanaveragepowerof60mWonmechanicalpropertieshavemadethemtargetsofexten-theupperdiamond.Themicroscopefocusedtheincidentsivestudy.Vibrationalspectroscopy,andRamanspectros-copyinpa
6、rticular,hasprovedtobeausefultoolinexamin-beamtoaspotsizeof50mmandthebackscatteredlightwasingthesestructures,9,11±20andtheoreticalwork2,7,8,21±27hascollected180°fromthedirectionofincidence.Theresolu-21producedmodelstoexplorethevibrationsofthetubesfortionofthespectrometeris
7、0.5cm.ACCDcameracooledvariousstructuresaswellastheinteractionsbetweenthewithliquidnitrogencollectedthedata,whichwasthenana-tubes.Asanexperimentalprobeofthetubeinteractions,Ra-lyzedusingaleast-squares®ttoasumofLorentzians.manspectroscopyathighpressureisaparticularlyfruitful
8、12technique.Inthispaper,wepresentahigh-pressureRamanstudyofsingle-walledcarbonnanotubebun
