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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.
In Plain English
The physical properties of matter are determined by the behaviour of its constituent atoms. Unfortunately, is it generally impractical, if not impossible, to exactly solve the quantum mechanical equation of motion pertaining to a system made up of large numbers of electrons and nuclei. Fortunately, there exist a great number of approximation techniques that allow us to make quantitative predictions about the properties of the various phases of matter we find in the Universe. I have recently used two such techniques, the diffusion Monte Carlo method and density functional theory, to study hydrogen under pressures more than a million times greater than found on the surface of Earth.
- Lattice dynamics and electron-phonon coupling calculations using nondiagonal supercells. Physical Review B 92 184301 (2015)
- Pseudopotential for the electron-electron interaction. Physical Review B 92 075106 (2015)
- Quantum Monte Carlo study of the phase diagram of solid molecular hydrogen at extreme pressures. Nature Communications 6 7794 (2015)