Structure of a 2∘ (010) Cu twist boundary interface and the segregation of vacancies and He atoms

A 2^∘ (010) Cu twist boundary is characterized by two sets of (1)/(2)<110> screw dislocations crossing at misfit dislocation intersections (MDIs). Molecular dynamics simulations show that between MDIs, dislocations split into the two possible {111} planes that share the <110> direction, forming a constriction where the glide planes change. Elasticity theory predicts the relative stability of such structures compared to structures without constrictions. Constrictions offer vacancy trapping sites that are lower in energy than those at the MDIs and with larger basins of attraction. For the substitutional He atom, MDIs and constrictions are comparable in energy. An off-lattice kinetic Monte Carlo code accounting for the presence of dislocations and their distortion fields shows that voids would form at the constriction points rather than at the MDIs. High-resolution experiments are needed to test the predicted structure.