HEAT-CONDUCTION AND RELAXATION IN LIQUIDS OF HIGH-VISCOSITY

The generalized hydrodynamic description of heat conduction in liquids of high viscosity is presented, following the phenomenological theory of thermoviscoelasticity. The theory applies in particular to undercooled one-component liquids near the glass transition, in which structural relaxation causes the specific heat to be frequency dependent. For a simple model in which a separate channel for the flow of configurational energy independent of phonons exists, it is shown that a frequency dependence of the thermal conductivity goes together with a wavevector dependence of the specific heat. The spectrum of the thermal entropy fluctuations and the quasi-elastic light scattering spectrum, which display the interference of the heat conduction mode with structural relaxation, are derived from the phenomenological equations. © 1990.