Energy and Atomic Configurations of Complete and Dissociated Dislocations. II. Screw Dislocation in an fcc Metal
Abstract
The arrangement of atoms around a screw dislocation in copper has been calculated by a variational method. The pairwise interaction between discrete atoms was represented by a Morse potential function. The displacements parallel to the dislocation line agree well with those given by linear elastic theory except for atoms within a distance of about 5.3 Å of the center of the dislocation. Because of this, there is a disparity between the atomistic and elastic energies inside a core radius of 5.3 Å for a complete <110> screw dislocation (Burgers vector=(a_{0}2)<110>), where a_{0} is the lattice parameter. The corresponding core energy is 1.0 eV per nearestneighbor distance. In the calculation of the complete dislocation, the atoms were not permitted to relax in a direction perpendicular to the dislocation line. This prevented dissociation. When this constraint is removed, dissociation into two partial dislocations occurs spontaneously. If the core is replaced by a hole of radius r_{eh} (the equivalent hole radius), the inside of which is hollow and outside of which linearelastic theory holds at all points, this radius is 1.1 Å. The energy of the screw dislocation varies as lnr at large radii, in agreement with elasticcontinuum theory. By comparing this asymptotic behavior with the corresponding curve for the edge dislocation, atomistic values of the shear modulus and Poisson's ratio were obtained.
 Publication:

Physical Review
 Pub Date:
 October 1966
 DOI:
 10.1103/PhysRev.150.448
 Bibcode:
 1966PhRv..150..448D