Simulation of radiation damage in gadolinium pyrochlores

We report molecular dynamics simulations of the production of radiation cascades in pyrochlores. We consider the apparently similar systems Gd 2 Ti 2 O 7 , Gd 2 Zr 2 O 7 and Gd 2 Pb 2 O 7 , the first two of which have been put forward as potential materials for high-level radioactive waste storage. The effects of changing the mass of the 'primary knock-on' atom are also examined and we investigate whether the change in behaviour from Ti to Zr to Pb is largely due to the mass or the size difference between the elements. Problems associated with analysing the cascades and the damage created are discussed. There are clear differences between the three compounds. The simulations see no direct amorphization but rather a transition to the fluorite structure which is more pronounced for the Zr and Pb compounds than the Ti system. Underlying chemical trends are examined.