Molecular dynamics simulation of a helium bubble bursting on tungsten surfaces

The bursting and expansion of helium bubbles near the surface of a tungsten material were investigated by using a molecular dynamics (MD) simulation. These helium bubble processes are considered to be important in the formation mechanism of fuzzy tungsten nano-structures. The phase diagram of the occurrence of bursting and expansion of helium bubbles was obtained by our MD simulation. The results of the simulation indicate that a helium bubble with a radius of 1.0 nm needs a high pressure of several tens of GPa to burst near the surface and to expand the bubble structures under the surface to the scale of ten nanometers. Moreover, from the viewpoint of the dynamics, the results of the MD simulation imply that the concavities and convexities observed on the surface in the early stage of the formation of a tungsten fuzzy nano-structure are caused by the bursting of the helium bubble.