Formation, migration, and clustering of delocalized vacancies and interstitials at a solid-state semicoherent interface

Atomistic simulations are used to study the formation, migration, and clustering of delocalized vacancies and interstitials at a model fcc-bcc semicoherent interface formed by adjacent layers of Cu and Nb. These defects migrate between interfacial trapping sites through a multistep mechanism that may be described using dislocation mechanics. Similar mechanisms operate in the formation, migration, and dissociation of interfacial point defect clusters. Effective migration rates may be computed using the harmonic approximation of transition state theory with a temperature-dependent prefactor. Our results demonstrate that delocalized vacancies and interstitials at some interfaces may be viewed as genuine defects, albeit governed by mechanisms of higher complexity than conventional point defects in crystalline solids.