Abstract:
:It is becoming common practice to partition glass-forming liquids into two classes based on the dependence of the shear viscosity η on temperature T. In an Arrhenius plot, ln η vs 1/T, a strong liquid shows linear behavior whereas a fragile liquid exhibits an upward curvature [super-Arrhenius (SA) behavior], a situation customarily described by using the Vogel-Fulcher-Tammann law. Here we analyze existing data of the transport coefficients of 84 glass-forming liquids. We show the data are consistent, on decreasing temperature, with the onset of a well-defined dynamical crossover η(×), where η(×) has the same value, η(×) ≈ 10(3) Poise, for all 84 liquids. The crossover temperature, T(×), located well above the calorimetric glass transition temperature T(g), marks significant variations in the system thermodynamics, evidenced by the change of the SA-like T dependence above T(×) to Arrhenius behavior below T(×). We also show that below T(×) the familiar Stokes-Einstein relation D/T ∼ η(-1) breaks down and is replaced by a fractional form D/T ∼ η(-ζ), with ζ ≈ 0.85.
journal_name
Proc Natl Acad Sci U S Aauthors
Mallamace F,Branca C,Corsaro C,Leone N,Spooren J,Chen SH,Stanley HEdoi
10.1073/pnas.1015340107subject
Has Abstractpub_date
2010-12-28 00:00:00pages
22457-62issue
52eissn
0027-8424issn
1091-6490pii
1015340107journal_volume
107pub_type
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