Edge dislocations are characterised by columns of atoms in tension or in compression in a plane normal to the dislocation, above and below the slip plane. Such dislocations are conventionally viewed end-on at high resolution in transmission electron microscopes, because the tensile and compressive displacements are clearly visible. Screw dislocations are characterised by equivalent atoms in the...

We report the first ab initio density-functional study of <111> screw dislocation cores in the bcc transition metals Mo and Ta. Our results suggest a new picture of bcc plasticity with symmetric and compact dislocation cores, contrary to the presently accepted picture based on continuum and interatomic potentials. Core energy scales in this new picture are in much better agreement with the Peie...

Large twist-angle grain boundaries in layered structures are often described by Scherk’s first surface whereas small twist-angle grain boundaries are usually described in terms of an array of screw dislocations. We show that there is no essential distinction between these two descriptions and that, in particular, their comparative energetics depends crucially on the core structure of their scre...

  Simultaneous mid third clavicle fracture and acromioclavicular joint dislocation is a rare combination injury, as a result of high-energy trauma. We report a patient with a middle third clavicle fracture and ipsilateral grade three-acromioclavicular joint dislocation, which is a rare combination. The patient wanted to get back to work as soon as possible, so the fracture was fixed with recons...

This paper presents an analytical solution for an orthotropic circular cross section bar with a magnetic coating weakened by multiple arbitrary oriented cracks under Saint-Venant torsion by means of the distributed dislocation technique. At first, the solution of the orthotropic bar with a magnetic coating weakened by a Volterra-type screw dislocation is achieved with the aid of the finite Four...

The mobility of dislocation in body-centered cubic (BCC) metals is controlled by the thermally activated nucleation of kinks along the dislocation core. By employing a recent interatomic potential and the Nudged Elastic Band method, we predict the atomistic saddle-point state of 1=2〈111〉 screw dislocation motion in BCC iron that involves the nucleation of correlated kinkpairs and the resulting ...

Numerous articles describing the changes in structure and mechanical response of metals and alloys induced by shock waves have been published in the past twenty years (I-3). Increases in the concentration of point (4) and line defects (5), formation of twins (6), martensite (7) and precipitates (8) have been observed in the residual structures. Smith (9) proposed the f i rs t model accounting f...

Large twist-angle grain boundaries in layered structures are often described by Scherk's first surface whereas small twist-angle grain boundaries are usually described in terms of an array of screw dislocations. We show that there is no essential distinction between these two descriptions and that, in particular, their comparative energetics depends crucially on the core structure of their scre...

Previous density functional theory (DFT) studies of the 1/3 h1 210i screw dislocation in titanium have shown metastable core structures depending on the initial position of the dislocation line. We investigate this problem by modeling a screw dislocation with two initial positions using both DFT and a modified embedded atom (MEAM) potential for Ti with flexible boundary conditions. Both DFT and...

Using QM-Sutton-Chen many-body potential, we have studied the 1⁄2a<110> screw dislocation in nickel (Ni) via Molecular Dynamics (MD) simulations. We have studied core energy and structure using a quadrupolar dislocation system with 3-D periodic boundary conditions. The relaxed structures show dissociation into two partials on {111} planes. The equilibrium separation distance between the two par...