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1、insightreviewarticlesSupercooledliquidsandtheglasstransitionPabloG.Debenedetti*&FrankH.Stillinger†‡*DepartmentofChemicalEngineeringand‡PrincetonMaterialsInstitute,PrincetonUniversity,Princeton,NewJersey08544,USA(e-mail:pdebene@princeton.edu)†BellLaboratories,LucentTechnologie
2、s,MurrayHill,NewJersey07974,USAGlassesaredisorderedmaterialsthatlacktheperiodicityofcrystalsbutbehavemechanicallylikesolids.Themostcommonwayofmakingaglassisbycoolingaviscousliquidfastenoughtoavoidcrystallization.Althoughthisroutetothevitreousstate—supercooling—hasbeenknownfor
3、millennia,themolecularprocessesbywhichliquidsacquireamorphousrigidityuponcoolingarenotfullyunderstood.Herewediscusscurrenttheoreticalknowledgeofthemannerinwhichintermolecularforcesgiverisetocomplexbehaviourinsupercooledliquidsandglasses.Anintriguingaspectofthisbehaviouristhea
4、pparentconnectionbetweendynamicsandthermodynamics.Themultidimensionalpotentialenergysurfaceasafunctionofparticlecoordinates(theenergylandscape)offersaconvenientviewpointfortheanalysisandinterpretationofsupercoolingandglass-formationphenomena.Thatmuchofthisanalysisisatpresentl
5、argelyqualitativereflectsthefactthatprecisecomputationsofhowviscousliquidssampletheirlandscapehavebecomepossibleonlyrecently.heglassystateisubiquitousinnatureand(forexample,duringannealingorageing)andfarbelowTg,1technology.Itiscrucialintheprocessingofisnotdiscussed.Thereaderi
6、sreferredtoanexcellentrecent28foods,thecommercialstabilizationoflabilereviewforathoroughcoverageoftheseandothertopics.3biochemicals,andthepreservationofinsect3Tlifeunderextremesofcoldordehydration.PhenomenologyofsupercoolingandglassformationWindowglass,composedmostlyofsand,li
7、meandsoda,isFigure1illustratesthetemperaturedependenceofaliquid’s4,9thebest-knownexampleofanengineeredamorphousvolume(orenthalpy)atconstantpressure.Uponcooling4solid.OpticalfibresaremadeofverypureamorphousbelowthefreezingpointTm,molecularmotionslowsdown.silica,occasionallycar
8、efullydoped.MostengineeringIftheliquidiscooledsufficientlyfast,cryst