Jonathan Lloyd-Williams

Research

I am interested in investigating the physical properties of materials by utilising first-principles quantum mechanical methods. I am currently using a combination of density functional theory (DFT) and the highly accurate diffusion Monte Carlo (DMC) method to calculate the electronic structure and atomic vibrational properties of a variety of solids. I was recently involved in a project to construct a theoretical phase diagram of solid molecular hydrogen at high pressures and low temperatures. We used structures found in DFT-based searches to model the experimentally observed phases and calculated the electronic ground state energies using DMC at pressures up to 400 GPa, to which we added anharmonic vibrational free energies calculated within DFT. We found that anharmonic effects are important in determining the relative stabilities of the structures.