Introduction Researches on dislocations in graphite have been carried out from the 1950s. For example, edge dislocations [1] and partial dislocations in the basal plane [2] have been observed by transmission electron microscopy (TEM). The spiral growth patterns which originate from the screw dislocation have been observed [3, 4]. Moreover, it was observed by atomic force microscope (AFM) that g...

Dislocation motion governs the strength and ductility of metals, and the Peierls stress (σp) quantifies dislocation mobility. σp measurements carry substantial uncertainty in face-centered cubic (fcc) metals, and σp values can differ by up to two orders of magnitude. We perform first-principles simulations based on orbital-free density functional theory (OFDFT) to calculate the most accurate cu...

It is well-known that the solution for a straight dislocation in an infinite medium does not depend on the cut along which the displacement discontinuity is imposed. This is also true for a semi-infinite medium, or any simply-connected region. The stress and strain fields, energy and dislocation forces are the same regardless of the cut. Only displacements differ in the region between the two c...

We introduce a novel approach to calculating the Peierls energy barrier (and Peierls stress) based on the analysis of the dislocation migration dynamics, which we apply to 1/2a〈111〉 screw dislocations in bcc Ta. To study the migration of screw dislocations we use molecular dynamics with a first principles based embedded-atom method force field for Ta. We first distinguish the atoms belonging to...

The correspondence theorem which relates the solutions of displacement boundary value problems in classical and couple stress elasticity is formulated and applied to derive the solutions for edge and screw dislocations in an infinite medium. The effects of couple stresses on the dislocation strain energy is evaluated for both types of dislocations. It is shown that within a radius of influence ...

We extend our recent simulation studies where a screw dislocation in face-centered cubic (fcc) Ni was found to spontaneously attain a low energy partially cross-slipped configuration upon intersecting a forest dislocation. Using atomistic (molecular statics) simulations with embedded atom potentials, we evaluated the activation barrier for a dislocation to transform from fully residing on the g...

Dislocation/stacking fault interactions play an important role in the plastic deformation of metallic nanocrystals and polycrystals. These interactions have been explored in atomistic models, which are limited in scale length by high computational cost. In contrast, multiscale material modeling approaches have the potential to simulate the same systems at a fraction of the computational cost. I...

We investigate the T (3)-gauge theory of static dislocations in continuous solids. We use the most general linear constitutive relations bilinear in the elastic distortion tensor and dislocation density tensor for the force and pseudomoment stresses of an isotropic solid. The constitutive relations contain six material parameters. In this theory both the force and pseudomoment stresses are asym...

The width, Peierls barrier and stress for shuffle screw dislocation in Si and Ge have been calculated by the improved P-N theory. The calculated widths are about 0.6b, b is the Burgers vector. The Peierls barriers for shuffle screw dislocations in Si and Ge are respectively about 3.61~4.61meV/Å and 5.31~13.32meV/Å, Peierls stresses are 1.40~2.07 meV/Å and 1.93~3.29 meV/Å. Our calculated results...

Molecular dynamics computer simulations have been employed with the Tersoff interatomic potential to examine the atomic structure of (a=2) h110i screw dislocations forming regular two-dimensional arrays in silicon. The main attention is focused on the atomic configurations of dislocation intersections. The dislocations are assumed to be undissociated, following HREM observations on the low-angl...