Vacancy dissociation in body-centered cubic screw dislocation cores

The interaction between screw dislocations and vacancies in body-centered cubic metals is investigated using molecular dynamics simulations. For thirteen different classical interatomic potentials, materials properties relating to vacancies, dislocations, and the interaction between the two are evaluated. The potentials include six for iron, two for molybdenum, and five for tantalum, and they are a mix of embedded atom method (EAM), modified embedded atom method (MEAM), and angular dependent potential (ADP) styles. A previously unknown behavior was identified during the interaction simulations. Out of the thirteen potentials investigated, ten predict a vacancy on the dislocation core to no longer remain as a discrete point defect, but rather to dissociate along the dislocation line. The structure of the dissociation is dependent on the potential and is characterized here. As this vacancy dissociation alters the core structure of the dislocation, it may prove to be a new mechanism for dislocation pinning and pipe diffusion.