Oxysalts, Intermetallics and Mineral Systematics

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Recent success in relating cation centroids in complex oxysalts to metal centroids in intermetallics has motivated me to explore complex structure types, some which occur in nature as large crystals, including dickinsonite, alluaudite, graftonite, griphite, triplite, triploidite and grischunite. Why do such complex structures exist in phases which often form large crystals? Dickinsonite structure type occurs in crystals up to 1 m3 and has 47 atoms in the asymmetric unit. The PI plans to seek out appropriate cell transforms for these structures, and the appropriate intermetallic for comparison. He hopes to predict the orientation of the lone pair, v, in an environment of coordinating anions. This exploits the fundamental Pauling electrostatic valence rules. It is believed that this approach will aid in sorting out the myriad plumbous oxysalt structures which are presently known. Finally, the volumetric contribution of v in the sulfosalt minerals can be rationalized.