Regular intergrowth relations

Crystals often intergrow with respect to a certain crystallographic orientation. The following intergrowth relations of two or more single crystals of the same species have been identified  

Preferential nucleation along edges or at corners should also be mentioned. The following are examples of regular intergrowth between crystals of different species  

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Exsolution, precipitation, and decomposition 145 Table 7.2 Regular intergrowth relations observed in minerals... 

Many new structure types, some related to known types, are yet to be found by suitable new methods as discussed by Rao in Chapter 3. For example, many regular intergrowth structures are little lower in free energy of formation than the separate-layer types standing alone and so can be quite difficult to attain. Nevertheless they may have unique and useful properties. 

Modular structures are those that can be considered to be built from slabs of one or more parent structures. Slabs can be sections from just one parent phase, as in many perovskite-related structures and CS phases, or they can come from two or more parent structures, as in the mica-pyroxene intergrowths. Some of these crystals possess enormous unit cells, of some hundreds of nanometers in length. In many materials the slab thicknesses may vary widely, in which case the slab boundaries will not fall on a regular lattice and form planar defects. 

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