Dissociated perfect dislocations in the field-ion image

The paper describes observations of dissociated total dislocations in iridium. Two modes of dissociation are identified, namely {111} Shockely and {110} Frank, and it is further shown that these two modes occur on one dislocation. This pattern of dissociation allows an unambiguous assignment of a Burgers vector to the dislocation. From the observed stacking-fault ribbon width at the surface tentative estimates of the stacking-fault energy have been made. From this it is concluded that the stacking-fault energy of iridium is of the order of several hundred ergs/cm2.