A study of irradiation effects in TiO2 using molecular dynamics simulation and complementary in situ transmission electron microscopy

BJ Cowen and MS El-Genk and K Hattar and SA Briggs, JOURNAL OF APPLIED PHYSICS, 124, 095901 (2018).

DOI: 10.1063/1.5045491

Understanding radiation damage in crystalline systems at the atomic scale is essential for the development of multi-scale predictive models for advancing nuclear science and engineering applications. State-of- the-art techniques used for investigating irradiation effects include molecular dynamics (MD) simulations, which can provide attosecond resolution of damage cascades over picosecond time scales, and in situ transmission electron microscopy (TEM), which can provide millisecond resolution in real-time. In this work, MD simulations and in situ TEM ion beam irradiation of crystalline TiO2 with 46 keVTi(1-) ions are performed and results are compared. The MD results show that the ratio of the titanium to oxygen defects evolves during the radiation cascade. The vacancies are produced mostly in the core, while self-interstitials are concentrated at the periphery of the cascade. Cluster analysis of the MD results confirms the formation of a void (or a cluster of vacancies) that contains as much as approximate to 10000 vacancies in the ballistic phase, compared to <1000 after annealing. The radial distribution functions and the simulated selected area electron diffraction patterns at the peak of the ballistic phase confirm the existence of a short-range order and medium-range order throughout the simulation. However, the long-range order reemerges after annealing of the cascade event in agreement with the in situ TEM ion beam irradiation experiments. The MD simulations and the experiments show no indication of amorphization. Published by MP Publishing.

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