Model for anomalous self-diffusion in group-IVB transition metals

A model for anomalous diffusion in the bcc phase of group-$\mathrm{IV}B$ transition metals is proposed, based on the identity of structure of the activated complex for diffusion and the basal plane of the low-temperature metastable $\ensuremath{\omega}$ phase. An expression for the diffusion coefficient is derived from a phenomenological free energy of formation of an $\ensuremath{\omega}$ embryo. Excellent agreement is obtained with experimental data for bcc Zr.