Modelling the properties of electron and hole polarons in materials

The strong coupling between electrons and phonons in some materials leads to the formation of small polarons (quasiparticles comprised of a localised electron and an associated polarisation field). Predicting the properties of polarons is an important fundamental problem as well as being relevant for technologically important phenomena such as magnetism, photoconductivity, dielectric response and reactivity. In this project you will employ first principles methods recently developed in our group to predict the formation and properties in a range of previously unexplored materials including oxides, nitrides and perovskites.
Density functional theory (DFT) is a first principles theory that allows the properties of materials to be predicted by solving (approximately) the quantum mechanical problem of a system of interacting nuclei and electrons. Although a very successful and popular approach most implementations of DFT suffer from self-interaction errors which make accurate description of polaronic behaviour challenging. In our group we have developed approaches to minimise this self-interaction error and applied them to model charge carrier trapping in bulk crystals, at surfaces and interfaces, and also to model exciton trapping and radiative and non-radiative recombination (mainly considering titanium dioxide as a model system). This project aims to develop these methods further to improve accuracy and capabilities and apply them to a range of materials where polaronic behavior is suspected but not yet explored.