On the diffusion mechanisms of helium in nickel

Abstract

Helium atoms in nickel at elevated temperatures exist primarily in substitutional sites, from which they may diffuse by a vacancy, dissociative, or exchange mechanism. The diffusion rates for these processes are calculated using the Embedded Atom Method. The dissociative mechanism is found to be dominant for all temperatures, provided that the vacancy concentration is not far above equilibrium. The activation energies involved in the different mechanisms are found to agree with activation energies derived from previous helium release experiments.