Atomistic Simulations on ˝<111> Screw Dislocation in BCC Ta

Guofeng Wang, Alejandro Strachan, Tahir Cagin and William A. Goddard III

Using the newly developed Embedded-Atom-Model (EAM) potential for tantalum (Ta), atomistic simulations were performed to investigated the core structure, core energy and Peierls energy barrier for ˝<111> screw dislocation. Equilibrated core structures were obtained by relaxation of dislocation quadrupoles with periodic boundaries. It was found that the equilibrium dislocation core had three-fold symmetry and spread out in three <112> directions on {110} planes. Core energy was determined to be 1.36 eV per Burger’s vector b. Motions of dislocation were studied in a dislocation dipole cell and Peierls energy barrier were computed: initial (static) Peierls potential was 0.08 eV per unit dislocation and dynamic Peierls potential was 0.06 eV per unit dislocation. Peierls stress was estimated to be about 0.03 m , where m is the bulk shear modulus of perfect crystal.