| Fragility and compressibility at the glass transition (2004) | |||||||||||
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| PHYSICAL REVIEW Fragility and compressibility the glass transition Buchenau and Wischnewski Institut Festk rperforschung Forschungszentrum lich Postfach lich Germany Received January revised manuscript received March published September Isothermal compressibilities and Brillouin sound velocities from the literature allow separate the compressibility the glass transition into high frequency vibrational and low frequency relaxational part Their ratio shows the linear fragility relation discovered ray Brillouin scattering though the data bend away from the line higher fragilities Using the concept constrained degrees freedom one can show that the vibrational part follows the fragility independent Lindemann criterion the fragility dependence seems stem from the relaxational part The physical meaning this nding discussed DOI PhysRevB PACS number Very recently Scopigno compiled ray Brillouin data glasses comparing the integrated Brillouin line intensity the intensity the central line They found linear relation between this ratio and the fragility log T ned terms the steep rise the viscosity towards the glass temperature with decreasing temperature the supercooled liquid This striking result poses two questions The rst more technical point Does the momentum transfer range the ray Brillouin technique still ect the long wavelength limit The second more fundamental the fragility related the Brillouin intensity the central line intensity Scopigno only demonstrate linear relation the rat | |||||||||||
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