Dr. Vanessa de Souza
Research Summary

Constraint Networks, Dynamic Heterogeneities And Relaxation In Disordered Solids

The inspiration for my current research was a desire to find the simplest possible model system that can still reproduce the complex dynamics found in supercooled liquids. Our model is based on a constraint network, in such a network we retain only topological information and have no information about geometry. A disordered network of bonds with a fixed configuration can relax via a variety of unconstrained motions. We use the Pebble Game algorithm of Jacobs and Thorpe [Phys. Rev. Lett. 75, 4051 (1995)] to decompose the system into separate rigid clusters and identify the remaining degrees of freedom. This simple model system can describe inherent structures on the potential energy surface for a variety of disordered solids. Characterisation of local soft modes or unconstrained motions allows us to examine dynamical heterogeneities in these solids, in the form of the spatial distributions of relaxation timescales. When bonds are allowed to change, we can also construct long-term relaxation functions and hence determine dynamical susceptibilities for an evolving system. Furthermore, we can consider the effects of temperature or density on relaxation.