CALTECH ASCI TECHNICAL REPORT 120 cit-asci-tr120 Kinks in a/2<111> Screw Dislocation in Ta

We study the structure and formation energy of kinks in 1/2a<111> screw dislocations in metallic Tantalum using molecular dynamics with a first principles based many-body interatomic potential. In our study, four a/3<112> kinks are in a quadrupole arrangement in the simulation cell. 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 8 distinguishable single kinks and 16 kink pairs. The different mismatches of the core configurations along <111> direction attribute to the variations in the formation energy for different type of kinks. Formation energies for all possible kinds of isolated single kinks and kink pairs have been determined. It was found that 0.730 eV was the lowest energy cost to form a kink pair in the a/2<111> screw dislocation in Ta.