The Burgers vector of a dislocation must correspond to an atomic repeat distance of the crystal structure. Moreover, the energy of a dislocation is proportional to the square of the magnitude of the Burgers vector, and therefore Burgers vectors tend to be as short as possible.

Based on these considerations, predict the Burgers vector for the two crystal structures whose unit cells are shown below. Specify both orientation and length of the Burgers vector. For example, the Burgers vector of dislocations in the FCC structure, would be given as a/2 , where a is the unit cell dimension (lattice parameter).

(a) (b)