The Skelton Research Group

First-principles materials modelling and structural dynamics

Welcome to the Skelton research group website

We are a theory group based in the School of Chemistry at the University of Manchester, UK.

We use a wide variety of theoretical modelling techniques to study materials ranging from inorganic semiconductors to molecular crystals and “hybrid” inorganic/organic systems. We are particularly interested in modelling and understanding structural dynamics in solids and their effect on material properties.

Atomistic modelling is one of the most important tools in modern Materials Science. High-level theoretical calculations using for example density-functional theory (DFT) are now routinely applied to help interpret and explain experimental results. More recently, the predictive power of DFT combined with high-performance computing (HPC) has made it feasible to design and discover materials in silico, providing researchers with new approaches to challenges such as sustainable (“green”) energy.

Routine atomistic modelling studies athermal (T = 0 K) structures where the atoms are assumed to be “frozen” to their crystallographic positions. This static approach works well for a number of problems, but can be a significant approximation for others.

Even at 0 K, zero-point vibrational motion adds to the thermodynamic free energy, and the subtle changes can be enough to stabilise one material phase over another. At non-zero temperatures, thermal expansion of the crystal lattice leads to progressive changes in structural, mechanical, electrical and optical properties, and becomes particularly important for “soft” materials and/or when materials are used in high-temperature applications. In some material systems, more complex “anharmonic” structural dynamics lead to very different properties to the average crystallographic structure and novel effects such as heavily-suppressed thermal conductivity.

o-MAPbI3-Mode-036.gif o-MAPbI3-Mode-040.gif
Animations of two lattice vibrations (phonon modes) in the hybrid halide perovskite methylammonium lead iodide (CH3NH3)PbI3 (MAPbI3). Coupling between the motion of the PbI3- cage and the MA+ cation suppresses the thermal conductivity and is an important contributor to its remarkable performance as a photovoltaic (PV) absorber.

The theory of lattice dynamics provides an efficient and straightforward framework for including dynamics in theoretical models. However, the computing power needed to perform lattice-dynamics calculations routinely and on complex systems is quite a recent development, so they are presently very under-exploited.

Our focusses on novel applications of lattice dynamics in materials modelling and includes using established theories to address new problems, extending theories to study new phenomena, making implementations of methods available to the community as open-source software, and strengthening links between theory and experiment.

We apply theoretical modelling techniques to a wide range of systems and problems, and we regularly work with experimental groups to validate our results and to help get the most insight from measurements.

The research page gives more detailed information about the current research in the group. You can also browse our recent publications. If you would like to find out more, or if you are interested in working with us, have a look at current opportunities or contact us.