Acta Crystallographica Section B

Structural Science

Volume 56, Part 6 (December 2000)

Acta Cryst. (2000). B56, 921-935 [doi:10.1107/S0108768100009514]

X-ray structure determination of the monoclinic (121 K) and orthorhombic (85 K) phases of langbeinite-type dithallium dicadmium sulfate

A. Guelylah, G. Madariaga, W. Morgenroth, M. I. Aroyo, T. Breczewski and E. H. Bocanegra

Abstract: The structures of the monoclinic and the orthorhombic phases of type I langbeinite Tl₂Cd₂(SO₄)₃ have been determined at 121 and 85 K, respectively, by X-ray diffraction. A precise analysis of these structures shows the existence of some differences compared to langbeinites of type II. The monoclinic structure differs very little from the high-temperature cubic structure and the distortion relating the monoclinic structure to the cubic one is very small. SO₄ tetrahedra seem to rotate under orthorhombic symmetry in the monoclinic phase. A symmetry distortion analysis of the ferroelectric monoclinic distortion discloses the importance of the secondary modes with orthorhombic symmetry, especially for the O atoms of the SO₄ groups.

Online 1 December 2000


	Structure factor file (CIF format) (262.7 kbytes) Contains datablock default

	Structure factor file (CIF format) (156.2 kbytes) Contains datablock default

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