Topological evolution underlying macroscopic stress relaxation in viscous liquids

Correlations between stress relaxation and topological evolution in viscous liquids are studied by means of molecular dynamics simulation. The local topology is determined through a gyration tensor and the orientation of its principal axis is used to monitor the fluctuation of particle connectivity. In this context, decorrelation of orientational ordering is found to be highly heterogeneous in space in a peculiar manner: At the shear stress relaxation time, the orientationally corelated and decorrelated regions partition the simulated system into two mutually connected, interpenetrating interspersions without self-intersection. We found the orientationally decorrelated subdomain in this sponge-like bicontinuous structure renders a channel which promotes the stress relaxation and therefore underlies viscoelasticity of amorphous materials.