A new approach was introduced for calculating the Peierls energy barrier, and Peierls stress; based upon an analysis of the dislocation migration dynamics. It was applied to a/2<111> screw dislocations in body-centered cubic Ta. In order to study the migration of screw dislocations, molecular dynamics were used; with a first-principles embedded-atom method force field for Ta. Firstly, atoms belonging to the dislocation core were distinguished on the basis of their atomic strain energies. The dislocation core was defined as being the 12 atoms with higher strain energies per Burgers vector. This definition was then applied to the moving dislocations, using the dynamics of a [1¯10] dipole of a ½<111> screw dislocation at 0.001K, to deduce the Peierls energy barrier, E, and Peierls stress, τ. From the dynamics of a dislocation dipole, it was deduced that E was 0.032eV and τ was 790Mpa (for twinning shear) and that E was 0.068eV and τ was 1430Mpa, for anti-twinning shear. These values were in good agreement with the results which were obtained by applying direct shear stresses. The present method offered insights with regard to dislocation migration, and permitted the determination of a continuous path for dislocation migration. It was found that, under twinning shear, the screw dislocation moved along a path at an angle of 8.5° with respect to the [1¯10] direction. For anti-twinning shear, it moved along a path at an angle of 29.5° with respect to the [1¯10] direction.

Calculating the Peierls Energy and Peierls Stress from Atomistic Simulations of Screw Dislocation Dynamics - Application to BCC Tantalum. G.Wang, A.Strachan, T.Çagin, W.A.Goddard: Modelling and Simulation in Materials Science and Technology, 2004, 12[4], S371-89