The image force on a dislocation near to an interface which separated 2 half-crystals with differing elastic moduli was investigated by means of computer simulations. The <001> screw dislocation and the (100) interface between 2 body-centered cubic crystals were chosen because the dislocation was undissociated and the anisotropic boundary conditions had an analytical form which permitted accurate calculation. In an homogeneous medium, the dislocation core was planar and extended on a {110} dense plane, but the core widths depended upon the type of atomic potential which was used. In order to construct the bicrystal, the same potential was used both media, but was multiplied by a factor which was equal to the desired ratio of the shear moduli. The study was restricted here to values of the factor which were slightly larger than unity and were sufficiently small for the lattice friction to remain everywhere larger than the image force. The dislocation was placed at distances from the interface which ranged from 0, to 6 times the lattice constant. The configuration and the total crystal strain energy were calculated for each stable position. The total crystal strain energy included, in addition to the strain energy that was estimated for the atomistic region, the elastic energy of the surrounding continuum. The calculated curve for the total crystal strain energy, as a function of the distance from the interface, differed appreciably from elasticity only in regions that were a few atomic distances from the interface. The image force on the dislocation, which was deduced from the computed energies, exhibited a broad peak in the interface region. The maximum was smaller than that deduced from linear elastic energies under the same conditions. The peak shape was similar to that which was deduced from a Peierls-based calculation, but atomistic simulations indicated a lower peak with a greater extension. It was found that these 2 quantities were related to the core width of the dislocation.

Atomistic Computation of the Image Force on a Dislocation in a Bicrystal – 1. Case of Small Difference between the Elastic Moduli of the Two Half-Crystals. P.Beauchamp, J.Lépinoux: Philosophical Magazine A, 1996, 74[4], 919-38