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The
Burgers vector associated with a dislocation is a measure of the lattice
distortion caused by the presence of the line defect. The diagram shows
the convention for measuring the Burgers vector. A circuit is made around
a dislocation line in a clockwise direction (top picture) with each step
of the circuit connecting lattice sites that are fully coordinated. This
circuit is then transferred to a perfect lattice of the same type. Because
of the absence of a dislocation within this circuit, it fails to close
on itself, and the vector linking the end of the circuit to the starting
point is the Burgers vector, b = QM.
The
Burgers vector defined in this way is a unit vector of the lattice if the
dislocation is a unit dislocation, and a shorter stable translation vector
of the lattice if the dislocation is a partial dislocation. |
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