MOTION OF A SCREW DISLOCATION IN A 2-DIMENSIONAL PEIERLS POTENTIAL

Motion of a screw dislocation in a crystal lattice occurs by kink pair formation in a two-dimensional Peierls potential. Employing the line- tension model of a dislocation, the saddle-point configuration of a no nplanar kink pair in three-dimensional space and the associated activa tion energy an calculated. The method is applied to a [111] screw disl ocation in a bcc lattice assuming a threefold periodic sinusoidal Peie rls potential in the (111) plane. In this potential the dislocation ca n nucleate a kink pair from one stable straight configuration towards any of the three adjacent ones. Depending on the direction of the appl ied stress the relative frequencies of the three activation processes determine the temperature dependence of the critical flow stress and t he direction of total slip. The calculations reproduce well the plasti c anisotropy of bcc transition metals.