By using a new first-principles embedded-atom method potential, molecular dynamics simulations were made of the core structure, core energy and Peierls energy barrier and stress for the a/2(111) screw dislocation. Equilibrated core structures were obtained by the relaxation of dislocation quadrupoles with periodic boundary conditions. It was found that the equilibrium dislocation core had 3-fold symmetry and spread out in three <112> directions on {110} planes. The core energy per Burgers vector was deduced to be equal to 1.36eV/b. Dislocation motion and annihilation were studied by molecular dynamics simulation of a periodic dislocation dipole cell, with <112> and <110> dipole orientation. In both cases, the dislocations moved in zig-zag fashion on primary {110} planes. The atoms which formed the dislocation cores were distinguished on the basis of their atomic energy. In this way, the core energy and position could be accurately defined not only for equilibrium configurations but also during dislocation motion. The Peierls energy barrier was deduced to be equal to 0.07eV/b, with a Peierls stress of 3% of the bulk shear modulus of the perfect crystal. The preferred slip system at low temperatures involved <112> directions and {110} planes.

Molecular Dynamics Simulations of 1/2a<111> Screw Dislocation in Ta. G.Wang, A.Strachan, T.Cagin, W.A.Goddard: Materials Science and Engineering A, 2001, 309-310, 133-7