Dr. Vanessa de Souza
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.