Tilt and Twist Boundaries
The simplest grain boundary consists of a configuration of edge dislocations between two grains.
The misfit in the orientation of the two grains (one on each side of the boundary) is accommodated by a perturbation of the regular arrangement of crystals in the boundary region.
Figure 16.3 shows some vertical atomic planes termination in the boundary and each termination is represented by an edge dislocation.