It is defined as "A

vector that denotes the

magnitude and direction of

lattice distortion associated with a

dislocation." (Callister,

**Materials Science and Engineering an Introduction**, 776)

The Burgers vector can be used to identify the nature of a dislocation in a crystalline structure. If the Burgers vector is parallel to the dislocation line, this indicates a screw dislocation. If, however, it is perpendicular, this indicates an edge dislocation. An angle other than these (other than 0, 90, 180, 270 degrees) is indicative of a mixed dislocation.

For a given dislocation line, which may change direction and nature in one crystalline lattice, the Burgers vector will remain the same. In metallic materials, the direction will be in a close-packed crystallographic direction, with magnitude equivalent to the interatomic spacing.

In face centered cubic and base centered cubic structures, the **Burgers vector** may be expressed as

**b**=(a/2)[*hkl*]

where **a** is the unit cell edge length and [*hkl*] is the crystallographic direction having the greatest linear atomic density. As some basic vector math will tell you, the magnitude of the vector is

|**b**|=(a/2)(h^{2}+k^{2}+l^{2})^{1/2}

And the direction is, of course, (**b**/|**b**|).

This information was derived from my **Materials Science and Engineering** lecture notes.