Atomistic Simulation of kinks for 1/2a<111> Screw Dislocation in Ta

Structure, formation energy and mobility of kinks in 1/2a<111> screw dislocation in metallic Ta have been investigated via low temperature (0.001K) molecular dynamics with a new, first principle based, Embedded-Atom-Model (EAM) potential. We studied a/3<112> kinks using a simulation cell containing four dislocations in a quadrupolar arrangement. We impose periodic boundary conditions in the directions perpendicular to <111> and fixed boundaries in the <111> direction. We find that two, energetically equivalent, core configurations for the 1/2a<111> dislocation lead to 16 distinguishable kinks. The different mismatches of core configurations along <111> direction lead to variations in kink formation energy. The lowest formation energy of a kink pair is determined to be 0.73 eV. We propose an explanation for such variation based on a detailed structure and energy analysis. We also calculate the activation energy for dislocation motion via the double kink mechanism from a dipole annihilation simulation. We help the nucleation of a double kink by introducing a vacancy in the path of one of the dislocations. We find that the migration energy for dislocation motion via double kink formation is 0.016 eV/b, which is more than four times lower than 0.073 eV/b associated with a straight, perfect dislocation moving collectively.