Define Burgers vector.

• A. The distance between lattice points
• B. The speed of dislocation motion
• C. The energy required to create a vacancy
• D. The vector that describes the magnitude and direction of lattice distortion around a dislocation

Answer: (D)

The Burgers vector is the vector that describes how the crystal lattice is distorted around a dislocation, including its magnitude and direction. You can think of it as what you’d gain by trying to walk a closed loop around a dislocation: in a perfect crystal, completing the loop lands you back at the starting lattice point, but with a dislocation you end up offset by this vector. It’s a fundamental, lattice-geometry property of the defect, independent of the path you choose to trace the loop.

Its size is typically on the order of a lattice parameter, and its direction tells you how the distortion sits relative to the dislocation line: for an edge dislocation, the Burgers vector is perpendicular to the dislocation line; for a screw dislocation, it is parallel to the line; for mixed dislocations, it lies at some angle between these.

This concept is distinct from simply the spacing between lattice points, from the speed at which a dislocation moves, or from the energy needed to create a vacancy. The correct description captures the specific lattice distortion caused by the dislocation.