High resolution transmission electron microscopy of dislocation core dissociations in gold and iridium

Abstract

Abstract The occurrence of brittle fracture in iridium has attracted significant attention in recent years and is thought to be related to the energetics of the dislocation core, in particular the extremely high unstable stacking energy. Although it is not experimentally possible to measure the unstable stacking energy, first-principles calculations have been used to predict both this and the stacking-fault energy. These calculations suggest that, despite large differences in stacking-fault energy and elastic constants, gold and iridium exhibit similar dissociation behaviours, with screw dislocations in both metals dissociated by approximately 1 nm. In the current study, high-resolution transmission electron microscopy (HRTEM) has been utilized to observe experimentally the arrangement of atomic columns surrounding dislocation cores. Deviations from perfect lattice sites have been measured, and experimental observations quantified through comparisons with image simulations. In the case of screw dislocatio...