It was proposed that, contrary to current opinion, Hägg’s rule could be applied to the analysis of the diffusion of 3d and other solutes in isotropic transition-metal host phases; provided that the crystal radii of the host lattice and solute atoms were properly defined. Hägg’s rule then constituted a necessary, but not sufficient, condition for interstitial diffusion in these systems. The correlation between activation entropy and enthalpy for solute diffusion in the above host phases could then be used to identify the Hägg parameters at which interstitial diffusion was observed. These were related to the elastic part of the activation enthalpy for interstitial solute diffusion.

H.Blank: Philosophical Magazine B, 1996, 73[5], 833-44