The nature of the faults in the dissociated 9R-phase at an incoherent twin boundary was considered. An analysis of the dislocation content of a 5-layer break in the normal ABC/BCA/CAB stacking sequence of the 9R-phase showed that this defect was associated with a secondary grain boundary dislocation with a Burgers vector of a/6[¯211]. Atomistic simulations of secondary grain boundary dislocations at the incoherent twin interface showed that the sign of the Burgers vector was important in determining the core structure of the dislocation. The resultant atomic structures and the 5-layer width of the fault could be explained by analysing the set of twinning dislocations that made up the boundary. Atomistic calculations also showed, in agreement with experimental observations, that a shear parallel to the interface caused an increase in the fault width that was associated with the growth of the 9R-phase.

Effect of Grain Boundary Dislocations on 9R Stacking Errors at an Incoherent Twin Boundary in Copper. D.L.Medlin, S.M.Foiles, G.H.Campbell, C.B.Carter: Materials Science Forum, 1999, 294-296, 35-42