We would like to congratulate Michael Cooper who was successful in the recent defence of his thesis entitled Atomic Scale Simulation of Irradiated Nuclear Fuel. His work focused on using static and molecular dynamics calculations to study the role of temperature and non-stoichiometry in conventional and advanced nuclear fuels. The project culminated in the development of a many-body potential model that was used to study the behaviour of mixed actinide oxide systems.
The Atomistic Simulation Group headed by Professor Robin Grimes is based in the Department of Materials at Imperial College London. We use various simulation techniques to predict the atomic scale mechanisms and processes underpinning material properties in order to improve the understanding and design of new materials.
The group uses both quantum mechanical and classical pair-potential approaches to study various systems including:
- Fuel cells.
- Nuclear fuel.
- Nuclear waste.
- Fusion materials.
The accepted manuscript of our new paper on gallium doping in LLZrO battery materials is now available online:
- R. Jalem, M.J.D. Rushton, W. Manalastas Jr, M. Nakayama, T. Kasuga, J.A. Kilner, and Robin W. Grimes, “Effects of Gallium Doping in Garnet-Type Li7La3Zr2O12 Solid Electrolytes ”, Chemistry of Materials (2015). doi:10.1021/cm5045122
The paper is the result of an ongoing collaboration between the group and Dr. Randy Jalem. Randy originally spent several months with us at Imperial whilst visiting us as a PhD student from Nagoya Institute of Technology (Japan) and we would like to thank him and the other authors for all their hard work in bringing this to completion.
- LLZrO is a candidate for use as solid electrolytes in battery applications.
- The effects of Ga doping on the structure are considered.
- Ga is found to stabilise the cubic phase.
- The connectivity of Li percolation networks in LLZrO are visualised.
Our latest paper is now available from the Journal of Nuclear Materials:
- M.W.D.Cooper, S.T. Murphy, M.J.D. Rushton and R.W. Grimes, “Thermophysical properties and oxygen transport in the (Ux,Pu1-x)O2 lattice”, Journal of Nuclear Materials, 461 206–214 (2015) http://dx.doi.org/10.1016/j.jnucmat.2015.03.024
In this paper we build upon a recent body of work using a many-body potential approach (see potentials page) to investigate the thermophysical and diffusion properties of actinide oxides. Using an updated version of the PuO2 parameter set we have studied the thermal expansion, specific heat capacity, oxygen diffusion and the oxygen point defect energies of (Ux,Pu1−x)O2. The results shows that the non-uniform cation lattice has a much smaller effect on the oxygen diffusion in (Ux,Pu1-x)O2 compared to (Ux,Th1-x)O2. This is expained in terms of the lattice parameter missmatch between the end member oxides and the role this plays in the defect energies.
In this update to our actinide potential model, adjustments have been made to the PuO₂ parameter set that enable the potential to reproduce the experimentally observed melting point.
Our latest paper on alloying additions in Zr is now available as a pre-print on arXiv:
- P.A. Burr, M.R. Wenman, B. Gault, M.P. Moody, M.Ivermark, M.J.D. Rushton, M. Preuss, L. Edwards and R.W. Grimes, “From solid solution to cluster formation of Fe and Cr in α-Zr”, arXiv preprint (2015). PDF
By combining ab-initio simulations with advanced experimental techniques we investigate the microstructural change of Zr alloys under irradiation Zr alloys are used as nuclear fuel cladding, and their integrity is crucial for the safe production of nuclear power. Of particular concern is the increase in corrosion that is observed when Fe and Cr particles (alloys additions) are dissolved. Dissolution of these particles is related to neutron irradiation, but the mechanisms by which this occurs is still unknown.
In this update to our actinides potential model, we have made a set of python scripts available supporting the use of the model within DL_POLY and to allow users to modify and extend the potentials for their own use in both LAMMPS and DL_POLY.
Our latest paper is now available from the Journal of Materials Chemistry A site:
- E.E. Jay, P.M. Fossati, M.J.D. Rushton and R.W. Grimes, “Prediction and Characterisation of Radiation Damage in Fluorapatite”, Journal of Materials Chemistry A, (2014) doi:10.1039/C4TA01707B
In this paper we performed threshold displacement energy calculations and full damage cascades for the fluorapatite structure using molecular dynamics in conjunction with effective pair potentials. Fluorapatite is being considered as a host for the long term immobilisation of halide bearing nuclear wastes. As a result it is important to understand how the apatite structure withstands and recovers from radiation damage. Of particular interest were the structural changes noted in our damaged structures: phosphate polyhedra were found to form polymer chains, typical of phosphate glasses, that were interwoven with the calcium metaprisms forming the backbone of the apatite structure. The coincidence of these amorphous and crystalline features should help in our further understanding of the long term durability of this material.
We pleased to announce the publication of our new paper on lithium diffusion within lithium lanthanum titanate:
- E.E. Jay, M.J.D Rushton, A. Chroneos, R.W. Grimes and J.A. Kilner, “Genetics of superionic conductivity in lithium lanthanum titanates”, Physical Chemistry Chemical Physics, (2014). doi:10.1039/C4CP04834B
Lithium lanthanum titanate (LLTO) is a material that shows high lithium diffusivity even at room temperature, this makes it of considerable interest for battery applications. In the present paper we set out to try and understand how the arrangement of lanthanum atoms within this material leads to LLTO’s beneficial properties. This was achieved by using a genetic algorithm to search for configurations with particularly high diffusivities. These were then examined to see what could be gleaned from their structure in order to unlock the key to LLTO’s beneficial properties. The paper can be found here.
We are please to announce a new publication in collaboration with ANSTO on the effect of radiation damage on the thermal conductivity of UO2 using our recently developed many-body actinide oxide potential.
A comparison of the damage profile predicted by the many-body potential is made against previous potential models. A significant degradation in thermal conductivity is then predicted as a consequence. The conductivity of amorphous UO2 is also calculated.