We are interested in how order appears in liquids and solids and the kinetics of these processes. We look at applying these insights into strategies for material design and fabrication while adding to our fundamental understanding of the physics of the material world.
Computer simulations provide a powerful tool for not just modelling the complexities of atomic order and cooperative dynamics in liquids and solids but also a way of expressing our theoretical pictures of what is happening without the need for abstract mathematics. Many familiar phenomena like the freezing of a liquid, the formation of a wetting film, the lubrication between two sliding surfaces or the creeping flow of a viscous gel contain open puzzles that we need to resolve so that we can understand why materials sometimes fail and how we can design and make better materials for our use. In our research we make use of the power and flexibility of computer modelling to answer fundamental questions about crystal growth, glass formation, the variety of structures found in non-crystalline solids and the how disordered liquids and gels flow.
We are working on a variety of computer-based projects that focus on the relationship between complex structures and the associated dynamics in liquids and solids.
We can control the atomic organization in a solid by growing it molecule by molecule via vapor deposition. We want to make use of the tendency for molecules to demix coupled with the ‘trapping’ of structure by a glass transition to generate new types of materials made of micro-patterns of composition by vapor depositing mixtures of different molecules.
How rigidity persists when thermal motions are present is a particularly challenging question. We are studying this important question by trying to extend a powerful picture of rigidity in granular materials (like sand piles) known as jamming theory to low temperature liquids of atoms or molecules. We are using a combination of computation and theory to understand how thermal fluctuations influence how particles restrain each other’s motion.
Molecular crystal grow at rates up to 10,000 times slower than our current theories predict. This is an important issue in the development of pharmaceuticals and energy storage devices based on phase change. We have identified the amount of entropy loss on freezing as the crucial factor and are currently developing new modelling tools to test theories of role of entropy loss in slow crystal growth.
Professor Peter Harrowell
Email: peter.harrowell@sydney.edu.au
