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Supercooled Water as the Rosetta stone for the "strong" vs "fragile" glassformer problem C. Austen Angell,
 

Summary: Supercooled Water as the Rosetta stone for the "strong" vs "fragile" glassformer problem
C. Austen Angell,
Arizona State University
Wateris famous forits anomalies, seen mostclearly in the supercooledliquid state.We noted1
that the rate at which supercooling liquidslose theirentropyoffusion,leadingto the
Kauzmann Paradoxin the case ofglassforming liquids,is a maximum in the case ofwater.
This and otherpropertiesmade waterthe most"fragile" ofliquids,bythermodynamic criteria.
But a parallelexamination of waternearits glasstransition temperature(Tg)revealed1
that,in
this lowertemperature range,water is the "strongest" ofliquids -even strongerthan silica.
Here we will argue,using experimentaldata andanalogies,that the static correlation length
for various fluctuationsthat playa criticalrole in water's behavior,reversesdirectionbetween
these two extreme temperature ranges ,and then showhowthis implies that strongliquidsgo
into the glasstransitionin the face ofa correlation lengththatdecreases as the transitionis
approached2
.Only forfragile liquids doesan increasing static correlation lengthdrive the
glass transition,and this lengthrelatesto enthalpyfluctuations,notdensityfluctuations -
which behave oppositely.In this phenomenology,waterservesas the Rosetta stone,speaking
the language ofstrongliquids at lowtemperatures nearTg and that offragile liquids at high
temperatures.It leadsus3

  

Source: Angell, C. Austen - Department of Chemistry and Biochemistry, Arizona State University

 

Collections: Materials Science; Chemistry