Mechanism of intrinsic diffusion in the core of screw dislocations in FCC metals – A molecular dynamics study

Abstract

The mechanism of self-diffusion in the absence of any pre-existing point defects (intrinsic diffusion) along an a/2 〈1 1 0〉 screw dislocation in FCC metals is studied using molecular dynamics simulations. High diffusivity along the dislocation core at elevated temperatures is found to be due to the constriction of partial dislocations, where a vacancy-interstitial pair forms. The two point defects separate and start to migrate along the core, giving rise to diffusion. Formation energy for both vacancy and self-interstitial are found to be much lower on the constricted node of partial dislocations compared to other atomic sites, indicating the important role of the constriction in enhancing the diffusion.