Nanocrystals and supracrystals are arrangements of highly-ordered atoms and nanocrystals, respectively. At the nanometer scale, from face centered cubic (fcc) tetrahedral subunits, either single fcc nanocrystals such as cubooctahedra and octahedra or decahedral and icosahedral nanocrystals are produced. Such nanocrystals with different shapes are produced by soft chemistry. At the micrometer scale, very surprisingly, supracrystals having shapes similar to those obtained at the nanometer scale are produced. For example, large triangular nanocrystals as well as supracrystals are produced either by soft chemistry, from nanocrystals diffusion on a surface or by nanocrystals interactions in solution. The morphologies of nanocrystals, supracrystals and minerals, which are similar at various scales (nm and mm), are pointed out and an explanation of these similarities is undertaken.
Source : Analogy Between Atoms in a Nanocrystal and Nanocrystals in a Supracrystal: Is It Real or Just a Highly Probable Speculation ? N.Goubet and M. P. Pileni. J. Phys. Chem. Lett., 2011, 2, 1024–1031.