Atomistic simulations of He bubbles in Beryllium

JQ Xi and YQ Shi and V Pronskikh and F Pellemoine and D Morgan and I Szlufarska, JOURNAL OF NUCLEAR MATERIALS, 576, 154249 (2023).

DOI: 10.1016/j.jnucmat.2023.154249

Formation of He bubbles can have a significant effect on the microstructural evolution and properties of irradiated materials. Here, we use atomistic simulations based on machine learning potentials to inves-tigate the fundamental behavior of He bubbles in Be, with a specific focus on the shape, stability, and diffusivity of bubbles. Stability of He bubbles is quantified in terms of formation energies, which are de-termined as a function of the ratio of He/V. We find that He bubbles become unstable with respect to plastic deformation through punch-out dislocations around the bubble when the He/V ratio is larger than <^>1.25, and the punch-out process induces the change of the regular bubble shape. In general, the bubble shape of He in Be is found to be ellipsoid-like. It is also found that for a fixed He/V ratio, the bubble attracts vacancies to become larger in size. If the bubble size is constant, the bubble attracts additional He atoms until the punch-out reaction occurs. The dominant diffusion mechanism of He bubbles changes from surface diffusion to volume diffusion as the temperature is increased, with a crossover occurring at about 900 K. (c) 2023 Elsevier B.V. All rights reserved.

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