Metastrengite mineral occurs as monoclinic modification of hydrated ferric orthophosphate FePO4·H2O. The orthorombic modification is known as strefigite. The space group of metastrengite is P 2 1/n and lattice parameters are: $a_{0} = 5.330 \pm 0.003$ Å ; $b_{0} = 9.809 \pm 0.004$ Å ; $c_{0} = 8.714 \pm 0.005$ Å ; $\beta = 90^\circ 36' \pm 8'$ according a new determination. The structure was determined from a three-dimensional Patterson function. The three-dimensional network is formed by isolated octahedra FeO4(H2O)2 and PO4 tetrahedra. The Fe-O and P-O average bond lengths are 2.00 Å and 1.53 Å respectively. Some relationships between metastrengite and strengite structures are given. The final discrepancy index R is 0.08, for 575 observed structure factors.
Referenze Bibliografiche
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Con il contributo del Ministero per i Beni e le Attività Culturali