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:

  • Energy Materials:
    • Fuel cells.
    • Batteries.
    • Nuclear fuel.
    • Nuclear waste.
    • Fusion materials.
  • Semiconductors.
  • Glasses.

Latest News

New Paper - "Thermal conductivity and energetic recoils in UO₂ using a many-body potential model"

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.

New Paper - "Peroxide defect formation in zirconate perovskites"

Our paper is now available from the Journal of Materials Chemistry A site:

In this paper we find a novel method for the accomodation of excess oxygen in ternary perovskite oxides. These materials are of high interest due to their proton conductivity and high temperature stability. For these properties, it is crucial to understand if the material may accomodate deviation from stoichiometry and what is the underlying mechanism. A peroxide substitution defects (i.e. two tightly bonded oxygen atoms replacing a single lattice oxigen) was predicted to be more favourable than conventional oxygen defects at low electron chemical potentials, as these can be accomodated without the need for a charge compensating species. In particular, for BeZrO3 this has important implicaitons as it reduces the solution energy of excess oxygen down to near 0 eV. These predictions were confirmed by Raman spectroscopy of BaZrO3 and SrZrO3 that were treated with H2O2.

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Updated details on actinide potential model: error-function for short range cut-off

The page describing the actinide potential model has undergone a minor update. The details of the short range cutoff on the EAM component of the model has been explicitly described. An error function is used to smoothly taper the density term of the EAM to zero at 1.5 Å.

In addition, to demonstrate that a smooth cutoff is achieved the full actinide oxygen interaction for PuO2 ThO2 and UO2 is plotted as a function of interatomic separation. Furthermore, the many-body nature of the model is shown by plotting this interaction with different numbers of coordinating oxygen atoms. The actinide-oxygen bond strength is progressively weakened as the coordination number increases.

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Actinide Potential Model Updated to Allow Simulation of Mixed Oxides

Our recently developed model for actinide oxides has been extended to allow simulations of actinide solid solutions opening the way to simulation of mixed oxide materials relevant to nuclear fuel materials. Learn about v1.1 of the model on actinide potentials page.

Please also see the related article in which the improved model was described:

  • M.W.D. Cooper, S.T. Murphy, P.C.M. Fossati, M.J.D. Rushton and R.W. Grimes, “Thermophysical and anion diffusion properties of (Ux, Th1-x)O2”, Proc. Royal Soc. A, 470 (2014) 20140427. doi: 10.1098/rspa.2014.0427.

New Paper - "A Concerted Mechanism for Cl Migration in Chlorapatite"

We are pleased to announce the publication of our new paper on Cl- diffusion in chlorapatite, a material that is being considered as a host for halide bearing nuclear waste:

  • M.L. Jackson, E.E. Jay, M.J.D. Rushton and R.W. Grimes, “A concerted mechanism for Cl- in chlorapatite”, Journal of Materials Chemistry A 2 (2014) 16157. doi:10.1039/C4TA03275F
Coupled migration sequence of two Cl− ions within a single anion channel at 1250 K over 0.64 ps viewed in (a) the  and (b) the  direction. The colour of the migrating ion denotes time such that ions of the same colour represent different ions at the same time. Cl− lattice sites are denoted by black dotted circles.

In this work the potential set previously developed for fluorapatite has been extended to include chlorine and thus chlorapatite. Previously, fluorine was observed to migrate in a quasi–1D concerted mechanism along channels in the fluorapatite [001] direction, with migration mediated by interstitial sites. Chlorine appears to migrate by a similar but distinct mechanism in chlorapatite, whereby instead of being mediated by interstitial sites migration proceeds directly along the [001] direction via a vacancy mediated mechanism, with several ions moving in concert. Vacancies are created through the formation of Frenkel pairs, with the interstitial position roughly equivalent to that of fluorine in fluorapatite.

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