The core structure of dislocations: Peierls model vs. atomic simulation

Recent atomic simulations of dissociated dislocations in the {1 1 1} plane of Ni are compared with the result of the Peierls model. It is shown that, even when the stacking-fault energy is held constant, small variations in secondary features of the interplanar potential (the γ-surface) can have a marked influence on the separation between the partial dislocations and their behaviour during displacement. Whereas the interplanar potential can be determined by ab initio methods, the interatomic potential used in simulations, although based on quantum mechanical considerations, is only semi-empirical. Therefore the values derived for the Peierls energy or Peierls stress by atomic simulations can only be considered as order of magnitude estimates.