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Slovakia, has been refi ned to an R 1 index of 4.90% for 5263 unique refl ections [F o 2 ≥ 2 (F 2)] measured with MoK␣ radiation on a three-circle diffractometer equipped with a CCD detector. There are 10 pure Pb and 8 Sb sites, as well as three mixed (Pb,Sb) and (Sb,Pb) sites and three split coordinations of Sb in the crystal structure. Thirty S positions and one presumed Cl position, designated as "S1", constitute the anion part of the structure. The structure is of a rod-layer type, with two types of rod-layers alternating along the stacking direction b. Dadsonite is a desymmetrized OD structure with profuse twinning. The two types of layers present possess layer symmetries p1 and b2/m11, respectively. These layers respectively have a pseudoperiodicity equal to a/2 and a set of elements of pseudosymmetry which together cause a disorder process.

Na4Mn4TisO18, formed at 1200 °C by crystallization from the composition NaMnTiO4, is orthorhombic, with unit-cell dimensions a = 9.268, b = 26.601, c = 2.888 fit. Mn3+ and Ti4+ atoms occupy octahedral positions, while the coordination of another Mn3+ is a rectangular pyramid. In this structure, groups of octahedra, joined by extensive edge and corner sharing, are linked together by the five-coordinated Mn3+ to leave a series of tunnels for the sodium ions. One of these is a single tunnel similar to that found in calcium ferrite; the other is a much larger one and contains sites for four sodium ions, only half of which are filled. The chemical composition was deduced from this structure analysis.

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