Transition from dislocation core spreading to dislocation dissociation in a series of B2 compounds

A comparative study of dislocation core structures was conducted in a serie s of BZ compounds. The dislocation cores were studied using atomistic compu ter simulation with embedded-atom method potentials. The results show a str ong dependence of the core structure on the values of the antiphase-boundar y (APB) energies of the compounds in the series. The [111] screw dislocatio ns were found to have planar cores in {110} planes. For very high APE value s, the cores are very compact. As the APE energies decrease, increasingly t wo-dimensional spreading of the cores was observed and ultimately dislocati on dissociation into partials. The partials are not exact 1/2[111] but corr espond to the actual minima of the gamma surfaces for these compounds. We s how that the dislocation coPes observed are best described as partly dissoc iated into partials with a continuous transition from dissociated to undiss ociated structures occurring as the planar fault energy increases. This is contrary to the view of dislocations being either dissociated or undissocia ted in a distinct sharp transition.