Thermally Activated motion of a Screw Dislocation in a Model B.C.C. Crystal

Abstract

Motion of a screw dislocation in a model b.c.c. crystal has been analyzed through the following procedure: (1) Peierls potentials for translations between stable and metastable positions of a screw dislocation are computed atomistically for a model crystal under various shear stresses on various planes, (2) activation energy of double kink nucleation for each translation is calculated using the theory based on the string model, and (3) the velocity and the integrated plane of thermally activated motion of a screw dislocation are analyzed for the steady motion. τ-χ and φ-χ relations obtained for a constant velocity at various temperatures show several characteristic features observed on transition b.c.c. metals; τ- T relations, however, give unrealistic discontinuous curves. τ-χ, φ-χ and also τ- T relations typical of less pure b.c.c. metals and alloys are reproduced by using a modified Peierls potential.