UoC crest

Jonathan Lloyd-Williams

Dr Jonathan Lloyd-Williams

Dr Jonathan Lloyd-Williams

EPSRC Doctoral Prize Research Associate

Postdoc in Prof Needs' group

Office: 543 Mott Bld
Phone: +44(0)1223 3 37466
Email: jhl50 @
Personal web site

TCM Group, Cavendish Laboratory
19 JJ Thomson Avenue,
Cambridge, CB3 0HE UK.

Research Image


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.

Research Image

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.