A dislocation-based description of grain boundary dissociation: application to a 90° 〈110〉 tilt boundary in gold

Abstract High resolution transmission electron microscopy (HRTEM) observations and atomistic simulations of {1 1 1}/{121} facets in a gold 90° tilt boundary show the presence of a ∼10 A wide layer with stacking faults distributed one to every three close-packed planes. This interfacial reconstruction, which forms the rhombohedral 9R stacking arrangement, is similar to that found previously for near−Σ=3{112} boundaries in low stacking fault energy metals. We discuss a general approach for partitioning grain boundary orientation into a set of Shockley partial dislocations and then apply this description to the {1 1 1}/{121} interface. The analysis explains both the distribution of faults and the geometry of the local plane bending and shows, further, that the 9R stacking occurs in both the Σ=3{112} and {1 1 1}/{121} interfaces due to the similar ratios of 30° and 90° Shockleys in both cases. Finally, we discuss limitations of this description, in particular concerning a 1/8[ 1 01] relaxation that is predicted by the atomistic simulations.