The mechanical response of deeply supercooled glassforming liquids

Speaker: Jurgen Horbach (University of Duesseldorf)

Abstract:

Glassforming liquids exhibit a dramatic slowing down of their dynamics with decreasing temperature. At very low temperature, i.e. far below the critical temperature of mode coupling theory Tc, they are in a transient amorphous solid state on a time scale that increases in an Arrhenius-like manner with decreasing temperature. Using non-equilibrium molecular dynamics (NEMD) simulation, we investigate different aspects of the mechanical response of this solid state. Simple pairwise-additive models such as binary Lennard-Jones potentials or soft-sphere potentials for non-additive polydisperse systems are considered. In active micro-rheology, one pulls a single particle through the system via a constant force. Far below Tc, an intermittent motion is observed which is reflected in a heterogeneous behavior of the trajectories of different pulled particles. While some of these particles are localized for a long time, others are very mobile and move in a relatively short time over long distances. We discuss to what extent this behavior can be explained in terms of a ‘depinning transition’. For sheared systems far below Tc, the solid-like response is associated with brittle yielding, as manifested by a sharp stress drop in the stress-strain relation and shear banding. By switching the strain rate during the shear, we elucidate the occurrence of memory effects that characterize the nonlinear transient response of deeply supercooled liquids.

This seminar will take place in room C4.174