A brief description of each type of defect is given below. In both pictures, the solid lines correspond to the crests of the stripe pattern. This is a characteristic property of disclinations. Note that the sense of rotation of the vector is different in the two diagrams.
Dislocations correspond to the insertion of an extra period in the stripe pattern.
The diagram on the right shows a sketch of a dislocation, where the crests of the stripe pattern appear as solid lines and the troughs as dashed lines. Note however that a vector locally perpendicular to the stripes is returned to its original orientation after one trip around the closed path. Line defects of stripe patterns are grain boundaries , which are curves separating regions of stripes with different orientations. Defects of hexagonal patterns Point defects of hexagonal patterns are penta-hepta pairs, which consist of one cell with five nearest neighbors paired to a cell with seven nearest neighbors. If one consider hexagons as resulting from the superposition of three stripe patterns, penta-hepta pairs appear to be due to the presence of two dislocations on two of the stripe patterns, as illustrated in the figure on the right.