(a) Bubble with 60 He atoms at 40°-GB. Blue and dark red points are He and W atoms, respectively. View is along [-111] direction. In panels (b)–(e), the potential difference and stress distribution of W atoms after He bubble has formed in sub-outermost and outmost atomic layer are shown. Sub-outermost atomic layers to He-bubble are shown in panels (b) and (d). The outmost atomic layer are shown in panels (c) and (e). Atoms are colored according to potential difference and stress respectively as indicated by color bars. View is done along [110] direction.