The structure of the a/2[111] screw dislocation was studied by means of high-resolution transmission electron microscopy and molecular dynamics simulations. Detailed analysis of high-resolution transmission electron microscopic images revealed, for the first time, the non-planar dissociation of the screw dislocation core; which was responsible for the high flow-stress of body-centered cubic metals at low temperatures. It was shown that the image contrast was dominated by surface relaxations which were introduced by the Eshelby twist. These relaxations did not correspond exactly to those predicted theoretically, but were influenced by the non-planar core-dissociation. It was concluded that molecular dynamics simulations were important for the interpretation of high-resolution transmission electron microscopic images of defects which led to shear stress components on the surface.

High-Resolution Electron Microscopy and Molecular Dynamics Study of the (a/2)[111] Screw Dislocation in Molybdenum. W.Sigle: Philosophical Magazine A, 1999, 79[5], 1009-20