The Mössbauer spectrum of synthetic hureaulite: Fe5
2+(H2O)4(PO4H)2(PO4)2 |
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Authors: | Angel Bustamante Enrico Mattievich Helio S de Amorim Ivo Vencato Máximo M Silveira |
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Institution: | (1) Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Apto. Postal 14-0149 Lima-14, Peru;(2) Instituto de Física, Universidade Federal do Rio de Janeiro, P.O. Box: 68.528, 21945-970 Rio de Janeiro, RJ, Brazil;(3) Instituto de Física, Universidade Federal de Goiás, P.O. Box 131, 74001-970 Goiania, GO, Brazil |
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Abstract: | The crystal structure of synthetic ferrous hureaulite, Fe5 2+ (H2O)4(PO4H)2(PO4)2, was refined from single-crystal X-ray data. It is monoclinic, space group C2/c, with a=17.487(4), b=9.017(2), c=9.338(2) Å, β=96.27(3)°, V=1463.6(6) Å3, Z=4 and D calc=3.327 g/cm3. This end member of the hureaulite series was crystallized under distinctly acidic conditions, by a method that gives perfect crystals, large enough for X-ray single crystal studies. The main feature of the hureaulite structure is that it has an equal number of normal (PO4)3+ and acid (PO4H)2+ tetradentate groups. These are centered on Fe2+ atoms and share corners with edge-linked octahedra, forming pentamer units. The five Fe2+ atoms are distributed on three distinct sites in these units. This can be directly observed in the Mössbauer spectrum at 295 K, which contains three doublets whose relative intensities correspond to the 1:2:2 distributions of crystallographic sites. |
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Keywords: | iron phosphate Hureaulite M?ssbauer Spectroscopy X-ray refinement |
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