Haegg's Rule and Fast Solute Diffusion in Cubic Transition Metal Phases

Abstract

Contrary to current opinion Haegg's rule can be applied in the analysis of the diffusion of 3d and other solutes in isotropic transition host phases like gamma-U, beta-Zr and Nb if the crystal radii of the host lattice and of the solute atoms are defined properly. A priori Haegg's rule then constitutes a necessary but not a sufficient condition for interstitial diffusion in these systems. Next the correlation between activation entropy and enthalpy of solute diffusion in the above host phases can be used to identify the Haegg parameters lambda-i at which interstitial diffusion is observed.