(642f) Mass Transport At Internal Interfaces of Inorganic Materials and Implications to Electrochemical Energy Systems

Interfaces of inorganic solids have gained prominence in electrochemical energy systems because of enhanced mass transport at interfaces as well as their ability to store a lot and retrieve quickly guest species. Despite several experimental observations, quantitive relations tying mass transport to interface structure are lacking. Since electrochemical energy systems are much complicated, we study simpler metal-metal interfaces as the first step. We use atomistic simulations to study the formation, migration, and clustering of delocalized vacancies and interstitials at several model metal-metal semicoherent interfaces. We find that point defects migrate between interfacial trapping sites through a multi-step mechanism that may be described analytically. Similar mechanisms operate in the formation, migration, and dissociation of interfacial point defect clusters. We show that effective mass transport rates may be computed using the harmonic approximation of transition state theory with a temperature dependent prefactor. Our results demonstrate that vacancies and interstitials at some interfaces may be governed by mechanisms of higher complexity than conventional point defects in crystalline solids. Implications of our studies to mass transport at grain boundaries and heterointerfaces of ceramics are discussed.