The crystal structure of perloffite

作者：Elliott P^*; Willis A C

来源：Mineralogical Magazine, 2011, 75(2): 317-325.

DOI：10.1180/minmag.2011.075.2.317

• perloffite
• crystal structure
• X-ray diffraction
• bjarebyite group

The structure of perloffite, ideally BaMn22+Fe23+(PO4)(3)(OH)(3), has been solved and refined from single-crystal X-ray data collected on a Sr-bearing sample from the Spring Creek copper mine, near Wilmington, South Australia. A fragment of the crystal used for the collection of the X-ray intensity data was analysed by electron microprobe. The resulting unit formula is (Ba-1.00,Sr-0.03)(Sigma 1.03) (Mn-1.15(2+),Fe0.762+Ca0.05Mg0.02,Na-0.01)(Sigma 1.99)(Fe1.943+Al0.06)(Sigma 2.00)(PO4)(2.99)(OH)(3.04). The structure is monoclinic, space group P2(1)/m, a = 9.2425(18), b = 12.470(3), c = 5.002(1) angstrom, beta = 100.19(3)degrees, V = 567.41(19) angstrom(3), Z = 2, and was refined to R-1 = 4.71% for 1568 unique observed reflections. The X site is [11]-coordinated and is occupied by dominant Ba and minor Sr, with an < X-O > distance of 2.953 angstrom. The M1 site is octahedrally coordinated and is occupied by Mn2+ and Fe2+ plus minor Ca, Mg and Na with an observed < M1-O > distance of 2.208 angstrom. The M2 site is also octahedrally coordinated and is occupied by Fe3+ plus minor Al with a < M2-O > distance of 2.018 angstrom. Perloffite is isostructural with other members of the bjarebyite group. Edge-linked [M2(2)O(6)(OH)(4)] dimers link via corners to form chains along [010]. Chains are decorated with PO4 tetrahedra and link in the a direction via [M1O(5)(OH)] octahedra and (Ba,Sr) atoms to form a complex framework. The H2 atom hydrogen-bonds strongly to the O3 anion, providing additional linkage between chains.

• 出版日期2011-4