Ab initio calculations of rare-earth diffusion in magnesium

We have used density-functional theory to calculate activation energies for diffusion of Al, Ca, and several rare-earth (RE) elements in Mg. The predicted solute-vacancy binding and exchange energies increase and decrease, respectively, with increasing solute size. Using the eight-frequency model for hcp lattices we determined correlation factors for each solute. Both Ca and all RE elements exhibit significant correlation effects whose temperature dependence can be described by an Arrhenius behavior. The correlation effects increase the activation energy, which for these solutes still remains below that for self-diffusion.