Spiral Patterns of Dislocations at Nodes in (111) Semi-coherent FCC Interfaces

In semi-coherent interface, a superposed network of interface dislocations accommodates the attendant coherency strains in the adjacent crystals and their intersections (referred to as nodes) can act as sinks and sources for point defects because of the low formation energy. Nodes in {1 1 1} semi-coherent interfaces are characterized with a spiral pattern (SP), wherein the line direction of each dislocation entering a node curves. The structure of SP nodes is able to switch between condensed and expanded by either reaction with point defects or mechanical deformation. Due to the switching of the node structures, point defect formation energies at nodes can be significantly reduced. Combining atomistic simulation and dislocation theory, these features are proven universal corresponding to the node density and the character of interface dislocations.