Multi-Timescale Investigation of Radiation Damage near TiO2 Rutile Grain Boundaries
Although grain boundaries (GBs) have been experimentally demonstrated to serve as sinks for absorbing radiation induced defects and improving the radiation tolerance of materials, the detailed atomistic interactions between defects and GBs leading to this enhanced tolerance are not well understood. In oxide ceramics the interactions are further complicated as defects can be charged and grain boundaries may exhibit space charge and charge dipole effects. Here, we use two atomistic modeling methods to examine the role of GBs in a model oxide system, rutile TiO2, in modifying defect production during irradiation events. The GB studied is a symmetric tilt GB with a rotation axis of [100] and a rotation angle of 15.25{sup o}. We use molecular dynamics to investigate defect production near the GB at both 300K and 1000 K and find that the damage production is sensitive to the initial distance of the primary knock-on atom (PKA) from the GB. We find three distinct regimes in which GBs have different effects on modifying defect production. Similar to GBs in metals, the GB absorbs more interstitials than vacancies at certain distances while this behavior of biased loading of interstitials diminishes at other distances. Further, we obtain the statistics of both interstitial and vacancy clusters 2 produced in collision cascades in terms of their compositions at two temperatures. We find that perfectly stoichiometric defect clusters (Schottky and anti-Schottky clusters) represent a small fraction of the total defect clusters produced. Moreover, a significant reduction in the number of interstitial clusters at 1000 K compared to 300 K is thought to be a consequence of enhanced migration of interstitials towards the GB. Finally the kinetic properties of certain defect clusters are investigated with temperature accelerated dynamics, without any priori assumptions of migration mechanisms. We find that small interstitial clusters become mobile at high temperatures while small vacancy clusters do not. Multiple migration pathways exist and are typically complex and non-intuitive. We use this kinetic information to explain experimental observations and predict their long-time migration behavior near GBs.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- DOE - SC
- DOE Contract Number:
- DE-AC07-05ID14517
- OSTI ID:
- 1040859
- Report Number(s):
- INL/JOU-11-23439; TRN: US201211%%220
- Journal Information:
- Philosophical Magazine, Vol. 92, Issue 12
- Country of Publication:
- United States
- Language:
- English
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