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The Burgers vector will be the vector to complete the circuit, i.e., from the start to the end of the circuit. [2] One can also use a counterclockwise Burgers circuit from a starting point to enclose the dislocation. The Burgers vector will instead be from the end to the start of the circuit (see picture above). [3]
In materials science, a partial dislocation is a decomposed form of dislocation that occurs within a crystalline material. An extended dislocation is a dislocation that has dissociated into a pair of partial dislocations. The vector sum of the Burgers vectors of the partial dislocations is the Burgers vector of the extended dislocation.
The dislocation has two properties, a line direction, which is the direction running along the bottom of the extra half plane, and the Burgers vector which describes the magnitude and direction of distortion to the lattice. In an edge dislocation, the Burgers vector is perpendicular to the line direction.
Apart from the Darwin width of the reflection, the width of single dislocation images may additionally depend on the Burgers vector of the dislocation, i.e. both its length and its orientation (relative to the scattering vector), and, in plane wave topography, on the angular departure from the exact Bragg angle. The latter dependence follows a ...
English: An illustration of the burgers vector in a screw and edge dislocation For more info, I highly recommend "The Physics of Semiconductors" by Marius Grundmann, DOI: 10.1007/978-3-642-13884-3 Date
The image can be further enhanced by tilting the crystal in different directions, which changes the orientation of the defects with respect to the electron beam. Under certain special diffraction conditions, dislocations can be imaged as narrow lines. The dislocation lines and Burgers vector can be determined for each dislocation. [2]
The dislocation line is presented in blue, the Burgers vector b in black. Edge dislocations are caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the adjacent planes are not straight, but instead bend around the edge of the terminating plane so that the crystal structure is perfectly ordered on either side.
The sessile nature of the Lomer–Cottrell dislocation forms a strong barrier to further dislocation motion. Trailing dislocations pile up behind this junction, leading to an increase in the stress required to sustain deformation. This mechanism is a key contributor to work hardening in ductile materials like aluminum and copper. [2]