Hole defects in the crystal structure of synthetic lipscombite (Fe{sub 4.7}{sup 3+}Fe{sub 2.3}{sup 2+})[PO{sub 4}]{sub 4}O{sub 2.7}(OH){sub 1.3} and genetic crystal chemistry of minerals of the lipscombite-barbosalite series
- University of Chicago (United States)
- Moscow State University (Russian Federation)
The crystal structure of a synthetic analog of the mineral lipscombite (Fe{sub 2.3}{sup 2+}Fe{sub 4.7}{sup 3+})[PO{sub 4}]{sub 4}O{sub 2.7}(OH){sub 1.3} obtained under hydrothermal conditions in the LiF-Fe{sub 2}O{sub 3}-(NH{sub 4}){sub 2}HPO{sub 4}-H{sub 2}O system is resolved (R = 0.040) by X-ray diffraction analysis (Bruker Smart diffractometer with a highly sensitive CCD detector, MoK{sub {alpha}} radiation): a = 14.776(3) A, b = 14.959(3) A, c = 7.394(1) A, {beta} = 119.188(4) deg., sp. gr. C2/c, Z = 4, {rho}{sub exp} = 3.8 g/cm{sup 3}, {rho}{sub calcd} = 3.9 g/cm{sup 3}. Fe{sup 2+} and Fe{sup 3+} cations are statistically distributed in each of four crystallographically independent positions, while occupying the corresponding octahedra with probabilities of 60, 90, 100, and 91%. The ratio Fe{sup 2+}/Fe{sup 3+} in the composition of the crystals was established by Moessbauer spectroscopy. Lipscombite is interpreted as a mineral of variable composition described by the formula (Fe{sub x}{sup 2+}Fe{sub n-x}{sup 3+})[PO{sub 4}]{sub 4}O{sub y}(OH){sub 4-y}. The field of stability is determined as a function of the iron content and the ratio Fe{sup 2+}/Fe{sup 3+}. It is shown that at n = 6 iron cations are ordered in octahedra and barbosalite structure is formed. An interpretation of genetically and structurally related members of the lipscombite family within a unified polysomatic series is proposed.
- OSTI ID:
- 21091484
- Journal Information:
- Crystallography Reports, Vol. 51, Issue 3; Other Information: DOI: 10.1134/S1063774506030072; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
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