First-Principles Study of Energetics of Helium Defects in Fe and Ni Metals

The formation energy and density of states of three kinds of helium defects in iron and nickel metals were calculated using the firstprinciples method based on projector augmented wave pseudopotential and generalized gradient approximation. The results show that the substitutional helium defects are the most stable, followed by the tetrahedral interstitial helium defects, and the octahedral interstitial helium defects are the most unstable in iron and nickel metals. It is suggested that the relative stability of helium defects in iron and nickel metals is governed by the electronic interactions between helium and the nearest neighboring metal atoms, rather than the elastic distortion of the defects.