The growth and release of helium bubbles near tungsten surface studied with molecular dynamics simulations
YL Zhou and CW Yuan and T Li and XM Tao and YF Ouyang, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 455, 66-73 (2019).
The growth and release processes of helium bubbles near tungsten surface have been investigated by molecular dynamics (MD) simulations. The results indicate that the surface morphologies are dependent on orientation of surfaces. Before bubble rupture occurs, stepped, thin schistose and pyramidal structures are observed on the (1 1 0), (1 0 0) and (1 1 1) surfaces, respectively. When the angle between the normal direction of surface and the sliding direction (<1 1 1> direction) is larger, flatter surface would be formed and the subsequent release process would be more violent. In the bursting process, the release rate of helium and the degree of surface damage are correlated with the surface stacking height before bubble bursts. Unrepaired crack structures have been observed on the (1 1 0) and (1 0 0) surfaces, while a smaller hole on the (1 1 1) surface. The stacking atoms have a tendency to make the surface restore to the bcc structure. At high temperature, the surface pore with radius similar to 1 nm can be self- healed from outer to inner by the diffusion of surface atoms, while no recovery is observed in MD time scale when the ratio of He/V in the bubble is high.
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