Disentangling density and temperature effects in the viscous slowing down of glassforming liquids

摘要

We present a consistent picture of the respective role of density andtemperature in the viscous slowing down of glassforming liquids and polymers.Specifically, based in part upon a new analysis of simulation and experimentaldata on liquid ortho-terphenyl, we conclude that a zeroth-order description ofthe approach to the glass transition should be formulated in terms of atemperature-driven super-Arrhenius activated behavior rather than adensity-driven congestion or jamming phenomenon. The density plays a role at aquantitative level, but its effect on the viscosity and the structuralrelaxation time can be simply described via a single parameter, an effectiveinteraction energy that is characteristic of the high temperature liquidregime; as a result, density does not affect the ``fragility'' of theglassforming system.