The Burgers vector for a mixed dislocation is oriented how relative to the dislocation line?

• A. Burgers vector is parallel to the dislocation line
• B. Burgers vector is perpendicular to the dislocation line
• C. Burgers vector is neither parallel nor perpendicular to the dislocation line
• D. Burgers vector is zero for mixed dislocations

Answer: (C)

A dislocation’s character comes from how the Burgers vector sits relative to the dislocation line. If the Burgers vector lies along the line, the dislocation is a screw; if it lies perpendicular to the line, it’s an edge. A mixed dislocation has a Burgers vector at an intermediate angle to the line, so it is neither parallel nor perpendicular. You can think of the Burgers vector as having two components: one along the line (screw component) and one perpendicular to the line (edge component). The magnitudes of these components are b_parallel = |b| cos(theta) and b_perp = |b| sin(theta), where theta is the angle between b and the dislocation line. The Burgers vector is nonzero for a dislocation, so a zero vector isn’t applicable.