Outer-sphere complex quasicrystal

Unit layers of smectites, notably montmorillonite, can associate in stacked, roughly parallel alignment to form a quasicrystal [52]. This particle structure is stabilized by attractive interactions between the basal planes of unit layers, as mediated by adsorbed cations and water molecules. The prototypical example of a montmorillonite quasicrystal is that comprising stacks of four to seven unit layers, with Ca2+ adsorbed in outer-sphere complexes on the siloxane surfaces to serve as molecular cross-links binding the unit layers together through electrostatic forces. This kind of quasicrystal appears to form with any bivalent cation and for any smectite [21,54]. 

In the case of bivalent metal cations, siloxane ditrigonal cavities tend to form outer-sphere surface complexes leading to quasicrystals, as described in Sec. 6.1. Since two ditrigonal cavities are involved, quasicrystal forma-... 

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