8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P8.32Thu 811:10-14:00Dynamic heterogeneities, boson peak and activationvolume in glass-forming liquidsVladimir Novikov, 1 Liang Hong, 2 and Alexei Sokolov 11 University of Tennessee, University of Tennessee, Department of Chemistry,1420 Circle Drive 37996, Knoxville, TN, United States of America2 Oak Ridge National Laboratory, Oak Ridge, TN, Ud States of AmThere are various arguments and models connecting the characteristic length associated with theboson peak vibrations x to the length scale of dynamical heterogeneity L het . x is usually definedas the ratio of the transverse sound velocity to the boson peak frequency. Here we present pressure,temperature and molecular weight dependencies of x, estimated using light scattering, in afew molecular and polymeric glass formers. These dependencies are compared with respectivedependencies of the activation volume ∆ ‡ V in the same materials. A good agreement is foundfor the pressure and molecular weight dependencies of x and ∆ ‡ V measured at the glass transitiontemperature T g . These results provide another evidence for a possible relationship betweensensitivity of structural relaxation to density (activation volume) and the heterogeneity volume.However, contrary to the expectations for L het , x does not decrease with temperature above T g inmost of the studied materials. The temperature dependence of x is compared to that of L het in glycerolestimated from literature data. The analysis shows a clear difference in behavior of x(T) and∆ ‡ V (T) at temperatures above T g , although ∆ ‡ V (T)1/3 and L het (T) have similar temperaturedependence. Possible reasons for the observed difference are discussed.32