Polymorphism synthetic approach

In summary, based on the available experimental and theoretical data, neither the existence nor the nonexistence of non-carbon fullerene polymorphs can be concluded. However, since sp bonding is energetically more favorable for Cn than for SIn, in the latter there are no caps and no plane structures which play a crucial role in fullerene formation. It seems that the mechanism of formation of such complexes for carbon and silicon is different. Taking into account the fact that the fullerene structure is not the global minimum for either carbon or silicon and in combination with the observable tendency of silicon clusters to have a spherical form, one can assume that under certain conditions processes similar to Stone-Wales rearrangement from polycyclic carbon structures to fullerene is also possible for silicon. Currently there is no common opinion on this issue. However, in addition to the notes about direct syntheses of non-carbon fullerenes, it is possible to specify some new synthetic approaches to the formation of silicon clusters. 

Various synthetic approaches have been applied to obtain stable and metastable Ga203 polymorphs, as either bulk crystalline phases or nanoparticles. Single crystals of the thermodynamically stable P-Ga203 phase can be obtained with and without dopants by using the Verneuil method, under oxidizing and reducing atmospheres [183,184]. 

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