Origin and spatial distribution of dislocations

In Fig. 6.5(b), it is seen that dislocations in the seed are inherited, and that only a small number of dislocations generate from the seed surface, whereas in Fig. 6.5(a) most of the dislocations are newly generated on the seed surface. These newly generated dislocations start from initial liquid inclusions trapped at etch pits. The dislocations originate due to the failure of matching of lattice planes when inclusions 

Not all the dislocations outcropped on a crystal surface are active growth centers. In Fig. 6.6, the distribution of growth hillocks on a (111) face of an as-grown Ba(N03)2 crystal is compared with the distribution of dislocations revealed by X-ray 

The most commonly encountered distribution of dislocations in crystals grown from solution or vapor phase (dilute ambient phases) by natural nucleation and without seed may be observed as dislocation bundles starting from the center of a crystal and running nearly perpendicular to the habit faces. In addition to these dislocations, smaller dislocation bundles originating from inclusions may be observed. See Figs. 6.1(e) and 6.5 for examples. 

Miyata, K. Tsubokawa, and M. Kitamura, Observation of synthetic emeralds by scanning cathodoluminescence method,/. Gemmol Soc., Japan, 18,1993, 3-14 

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