It was recalled that simple atomic jumps reversibly transformed thermal defects on crystalline surfaces, in the form of adatoms and advacancies, into interstitials and vacancies that constituted the thermal point defects of the bulk. The consequent coupling of bulk, surface and edge diffusion was treated here. It was demonstrated, as an exact result, how the bulk, surface and edge processes entered into a single eigenvalue problem that described, using orthogonal eigenvectors, combined relaxation of the bulk, surface and edge defects towards the non-uniform defect distribution at thermal equilibrium. The manner in which long-range surface flow mixed degenerately with bulk modes was explained, and the principle was extended to local surface modes in which fast surface processes diverged from the slower bulk modes. Bulk diffusion modes bound to surfaces, and driven by surface energetics, reproduced the results of Mullins for surface smoothing by surface and bulk diffusion. Analogous results for the coupling of surface and bulk diffusion to edge diffusion along surface steps were also obtained. The significance of the results was illustrated by numerical examples that used a new universal model for diffusion in metals and on metal surfaces.

Coupling Among Bulk, Surface and Edge Diffusion. C.P.Flynn: Physical Review B, 2006, 73[15], 155417 (12pp)