Crystallization cooperative bond ordering

In the crystalline version of smectic B, there is positional as well as bond-orientational order, and this ordering is called hexagonal, as opposed to hexatic. In the tilted version of the hexatic smectic B, there are two different directions the tilt has been found to take with respect to the hexagonal bond orientation, namely toward nearest and toward next nearest neighbors, producing the two different smectics I and F (see Fig. 10-27). Similarly, there are two different tilted crystalline hexagonal phases, smectics J and G. Even in smectic crystals, the molecules retain freedom to rotate cooperatively about theii axes, hence smectic ciystals are not as solid as most simple crystals. Nature is wonderfully creative in contriving... 

In recent years, ionic assemblies have received significant attention for [2 -I- 2] cycloaddition reaction in the solid state for several reasons greater stability due to robust and directional charge assisted H-bonded ionic heterosynthons over their neutral assemblies combination of more than one cooperative non covalent interaction in order to stabilise crystal packing, better control of the stoichiometry better solubility and easy separation of the photoproduct from the ionic auxiliary template. 

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