Role of Crystal Structure in Diffusion. II. Activation Energies for Diffusion in Closest-Packed Structures

Abstract

The effect of available diffusion paths on activation energies are considered for silver iodide, zinc oxide, and bismuth selenide. It is shown that the energy in β‐AgI should be nearly twice that in γ‐AgI because the Ag atoms in tetrahedral sites first must be displaced to octahedral voids before voidal diffusion can occur in the beta modification. The 2:1 ratio between the self‐diffusion energies of Zn determined by radioactive tracer and electrical conductivity measurements in ZnO is similarly explained. It is also shown that the difference between the activation energies for diffusion in BiSe and Bi₂Se₃ can be used to determine the formation energy of vacancies in BiSe. The agreement between these predictions and experimentally determined values attests that qualitatively accurate explanations can be based on considerations of the crystal structure.