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

Abstract

Abstract A comparative study of dislocation core structures was conducted in a series of B2 compounds. The dislocation cores were studied using atomistic computer simulation with embedded-atom method potentials. The results show a strong dependence of the core structure on the values of the antiphase-boundary (APB) energies of the compounds in the series. The 〈111〉 screw dislocations were found to have planar cores in {110} planes. For very high APB values, the cores are very compact. As the APB energies decrease, increasingly two-dimensional spreading of the cores was observed and ultimately dislocation dissociation into partials. The partials are not exact ½ 〈111〉 but correspond to the actual minima of the γ surfaces for these compounds. We show that the dislocation cores observed are best described as partly dissociated into partials with a continuous transition from dissociated to undissociated structures occurring as the planar fault energy increases. This is contrary to the view of dislocations bein...