Diffusion behaviors of helium atoms at two Pd grain boundaries

The diffusion behaviors of helium atoms at two symmetric grain boundaries (Σ5<001>{210} and Σ3<110> {112}) of Pd were investigated using molecular dynamics simulations through an analytical embedded-atom method(MAEAM) model. The simulations demonstrate that the interstitial helium atoms are easily trapped at the grain boundaries and precipitated into clusters. Due to the closed-shell electronic configurations of both helium and palladium, Pd grain boundaries yield strong capability of retaining helium atoms. By calculating the mean square displacements(MSD) of an interstitial helium atom at the grain boundaries, the diffusion coefficients were determined, and the linear fits to Arrhenius relation. The diffusion activation energies of interstitial helium atom at these two Pd grain boundaries were also evaluated.