Atomistic behavior of helium–vacancy clusters in aluminum

We have performed a molecular dynamics (MD) technique to calculate the formation energies of small HenVm clusters in Al using the embedded atom method (EAM), the Baskes–Melius potential and the Lennard-Jones potential for describing the interactions of Al–Al, Al–He and He–He, respectively. The binding energies of an interstitial He atom, an isolated vacancy and a self-interstitial Al atom to a HenVm cluster are also obtained from the calculated formation energies of the clusters. All the binding energies mainly depend on the He–vacancy ratio (n/m) of clusters rather than the clusters size. The binding energies of a He atom and an Al atom to a HenVm cluster decrease with the ratio, but the binding energy of a vacancy to a HenVm cluster increases with the ratio. The results indeed show that He atoms can increase the binding energy of a vacancy to a HenVm cluster, and decrease the binding energies of a He atom and an Al atom to the cluster, namely, He atom acts as a catalyst for the formation of HenVm clusters.