The Nye tensor characterized the strength of infinitesimal dislocations at each point in a continuously dislocated crystal, and provided a measure of the Burgers vector and the extent of dislocation dissociation. That description was used here in order to analyze ½<111> screw dislocations in body-centered cubic Mo obtained by using Finnis-Sinclair, bond order potential and first-principles simulations to detect misfit in the core region. The spatial distributions and strength of the fractional dislocations were calculated and compared for the various simulated core structures. The Nye tensor technique was also applied to high-resolution electron microscopic images of end-on screw dislocations in Mo in order to detect the edge fractional dislocations predicted by simulations. The advantage of the Nye tensor for this purpose arose from its insensitivity to the Eshelby twist due to surface relaxation in a thin transmission electron microscope foil. This was not true of other methods of depicting misfit: such as direct and differential displacement maps. Although the Eshelby twist was removed from the experimental high-resolution electron microscopic images, some residual mottled contrast was observed in the Nye tensor plots. This was due to experimental noise, which masked the true structure of the dislocation core and prevented the experimental characterization of screw dislocations in Mo by high-resolution electron microscopy.

Use of the Nye Tensor in Analyzing HREM Images of BCC Screw Dislocations. B.G.Mendis, Y.Mishin, C.S.Hartley, K.J.Hemker: Philosophical Magazine, 2006, 86[29-31], 4607-40