Nonlinear Hydrodynamics of a Hard Sphere Fluid Near the Glas(5)
时间:2025-03-09
时间:2025-03-09
We conduct a numerical study of the dynamic behavior of a dense hard sphere fluid by deriving and integrating a set of Langevin equations. The statics of the system is described by a free energy functional of the Ramakrishnan-Yussouff form. We find that th
theMCtheoriesprovideaqualitativeunderstandingofanumberofexperimentallyob-servedfeaturesofglassyrelaxation.However,someofthedetailedMCpredictionsarenotinagreementwithexperiments17andtheMCdescriptionclearlyfailstoaccountforthebehaviorobservedattemperaturesclosetoandlowerthanTc.Itisgenerallybe-lieved3thatthisfailurearisesfromthefactthatMCtheoriesdonottakeintoaccountactivatedprocessesinvolvingtransitionsbetweendi erentlocalminimaofthefreeenergywhicharesupposedtodevelopasthetemperatureisloweredbelowtheequilibriumfreezingtemperature.
IncontrasttoMCtheorieswhichportraytheglasstransitionasbeingpurelydy-namicinnature,therehavebeenanumberofattempts18 21todevelopa‘thermody-namic’theoryinwhichsomeoftheinterestingbehaviorobservedneartheglasstransitionisattributedtoanunderlyingcontinuousphasetransition.Theseattemptshavebeenmotivatedbythefactthattheobservedgrowthoftherelaxationtimeinso-called‘fragile’liquids2iswell-describedbytheVogel-Fulcherlaw
t=τse aT022:
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