Theory of small clusters of helium in metals

The development of the atomistic theory of small clusters of helium in metals is briefly reviewed with particular regard to the necessary interatomic potentials. The activation energy for interstitial helium motion is then calculated using He-Ni potentials which vary in their derivation from empirical to quantum mechanical (including the effects of the solid). Additional comparisons are made for single helium associated defects in Al where results using metal-metal potentials derived from pseudopotential theory and by empirical means are shown to give rise to only negligible differences. Finally, the theory is applied to the self-trapping of helium in metals, the formation of helium bubbles and associated self-interstitial loops. (author)