Lattice dislocation near a surface

The lattice model for a screw dislocation and for an edge dislocation near a surface and parallel to it are obtained. It has been shown that η/d, which is taken as the width of the dislocation for a Peierls-Nabarro dislocation, increases as the edge or the screw dislocation approaches the surface. The properties of the lattice dislocations are derived. The attractive image stress acting on the dislocation is obtained.