To understand the interactions between defects and grain boundaries (GBs) in oxides, two atomistic modelling methods were used to examine the role of GBs in a model system, rutile, in modifying radiation-induced defect production and annealing. Molecular dynamics was used to investigate defect production near a symmetric tilt GB at both 300 and 1000K. The damage production was found to be sensitive to the initial distance of the primary knock-on atom from the GB. Three distinct regimes were found in which GBs had different effects. Similar to GBs in metals, the GB absorbs more interstitials than vacancies at certain distances while this behaviour of biased loading of interstitials diminishes at other distances. Furthermore, the statistics of both interstitial and vacancy clusters produced in collision cascades were obtained in terms of their compositions at two temperatures. Perfectly stoichiometric defect clusters represented a small fraction of the total clusters produced. Moreover, a significant reduction in the number of interstitial clusters at 1000K compared to 300K was thought to be a consequence of enhanced migration of interstitials towards the GB. Finally, the kinetic properties of certain defect clusters were investigated with temperature accelerated dynamics, without any a priori assumptions of migration mechanisms. Small interstitial clusters become mobile at high temperatures while small vacancy clusters do not. Multiple migration pathways exist and were typically complex and non-intuitive. This kinetic information was used to explain experimental observations and to predict their long-time migration behaviour near to GBs.

Multi-Timescale Investigation of Radiation Damage near TiO2 Rutile Grain Boundaries. Bai, X.M., Uberuaga, B.P.: Philosophical Magazine, 2012, 92[12], 1469-98