title: Temperature fluctuations and the thermodynamic determination of the cooperativity length in glass forming liquids.
abstract: The aim of this paper is to decide which of the two possible thermodynamic expressions for the cooperativity length in glass forming liquids is the correct one. In the derivation of these two expressions, the occurrence of temperature fluctuations in the considered nanoscale subsystems is either included or neglected. Consequently, our analysis gives also an answer to the widely discussed problem whether temperature fluctuations have to be generally accounted for in thermodynamics or not. To this end, the characteristic length-scales at equal times and temperatures for propylene glycol were determined independently from AC calorimetry in both the above specified ways and from quasielastic neutron scattering (QENS), and compared. The result shows that the cooperative length determined from QENS coincides most consistently with the cooperativity length determined from AC calorimetry measurements for the case that the effect of temperature fluctuations is incorporated in the description. This conclusion indicates that-accounting for temperature fluctuations-the characteristic length can be derived by thermodynamic considerations from the specific parameters of the liquid at glass transition and that temperature does fluctuate in small systems.
authors.affiliation: Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock, Germany.
authors.forename: Y Z
authors.initials: YZ
authors.lastname: Chua
authors.affiliation: Jülich Centre for Neutron Science, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: R
authors.identifier: 0000000173218404
authors.initials: R
authors.lastname: Zorn
authors.affiliation: Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany.
authors.forename: O
authors.identifier: 0000000167467965
authors.initials: O
authors.lastname: Holderer
authors.affiliation: Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock, Germany.
authors.forename: J W P
authors.identifier: 0000000254146860
authors.initials: JW
authors.lastname: Schmelzer
authors.affiliation: Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18051 Rostock, Germany.
authors.forename: C
authors.identifier: 0000000167365491
authors.initials: C
authors.lastname: Schick
authors.affiliation: Wachbergstr. 3, 01326 Dresden, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Donth