Structure of manganese(3+) phosphate monohydrate by synchrotron x-ray powder diffraction

Abstract

The crystal structure of MnPO/sub 4/ x H/sub 2/O has been determined from high-resolution synchrotron X-ray powder diffraction data. The powder pattern was indexed on the basis of 20 accurately measured reflections by an automatic indexing program. Integrated intensities were obtained for 61 unambiguously indexed reflections and used to generate a Patterson map from which the position of the manganese atom was determined. The remaining non-hydrogen atoms were located by Fourier methods, and the hydrogen atom was placed geometrically and refined without constraints. Refinement of the entire diffraction profile, by the Rietveld method, converged to final agreement factors R/sub wp/ = 0.161, R/sub p/ = 0.122, and R/sub I/ = 0.047. The compound crystallizes in the monoclinic space group, C2c, with lattice parameters a = 6.912 (1) A, b = 7.470 (1) A, c = 7.357 (1) A, ..beta.. = 112.3 (1)/sup 0/, and Z = 4. The structure consists of axially distorted MnO/sub 6/ octahedra linked together, through the oxygen atom of the water molecule at a common vertex, to form zigzag-Mn-O-Mn-chains running parallel to (101). These chains are interconnected by PO/sub 4/ tetrahedra to form a continuous three-dimensional network. 27 references, 5 figures, 2 tables.