Atomistic simulations, involving a modified generalized pseudopotential theory potential and Green’s function boundary conditions, were used to determine the Peierls stress of rigid straight (a/2)<111> screw dislocations for shear stresses applied to {110}- and {112}-type planes. It was found that the Peierls stress of (a/2)<111> screw dislocations, for a shear stress applied to the {110} planes, ranged from 0.0175μ to 0.020μ. A large twinning/anti-twinning asymmetry was found for the application of a pure shear stress to the {112} planes; with the Peierls stress along the twinning direction ranging from 0.0125μ to 0.020μ and that along the anti-twinning direction ranging from 0.050μ to 0.0562μ. The Peierls stresses of screw dislocations, for tensile and compressive stresses applied along {001}, {110}, {111} and {201} directions, were also determined. A large tension/compression asymmetry was observed for the {001}, {110} and {111} directions. This was a reflection of the twinning/anti-twinning asymmetry observed in pure shear stress calculations. A tension/compression asymmetry was also observed for the {201} direction; thus indicating that non-glide stress effects were also important in determining the Peierls stress. In order to increase the understanding of (a/2)<111> screw dislocation motion via the kink pair mechanism, the core structures and energetics of 6 possible kinks and 2 antiphase defects on (a/2)<111> screw dislocations were also determined. It was found that the kink pair formation energy, at infinite separation, varied from 1.46 to 2.10eV. This range was in reasonable agreement with the experimental value of 1.27eV.

Atomistic Simulations of (a/2) <111> Screw Dislocations in BCC Mo Using a Modified Generalized Pseudopotential Theory Potential. S.I.Rao, C.Woodward: Philosophical Magazine A, 2001, 81[5], 1317-27