Formation energies of helium-void complexes in nickel

The Embedded Atom Method (EAM) has been used to calculate the formation energies of small voids (containing helium) in nickel. The binding energies of helium and vacancies to the helium-void complexes are also determined. Helium is strongly bound to helium-void complexes (up to 4 eV binding energy), and high helium densities significantly increase vacancy binding energies. Thus, the effect of helium is to stabilize small voids. The formation energy of small helium-void complexes can be separated into two parts, the energy to create the empty void and a residual energy associated with the helium atoms. The latter is shown to primarily arise from the long-range interactions of the helium atoms with the surrounding metal atoms rather than from short-range helium-helium interactions.