Anomalous shape effect of nanosized helium bubble on the elastic field in irradiated tungsten.

Bubble pressure and elastic response in helium-irradiated tungsten are systematically investigated in this study. An anomalous shape effect is found that the radial normal stress and mean stress distributions around a nanosized void or bubble are far from the spherical symmetry, which is ascribed to polyhedral geometry characteristic of the nanosized bubble and physical mechanism transition from crystal surfaces dominated to the surface ledges and triple junctions dominated. Molecular simulation shows that Young-Laplace equation is not suitable for directly predicting equilibrium pressure for nanosized bubble in crystals.