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Introduction. Several modifications [see Hulliger (1976) for a review] are known for tantalum disulfide, the forms extensively studied being 1T-TaS2, space group P3ml [Cd(OH)2-type structure], with Ta in octahedral coordination by S, and 2H-TaS2, space

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Single-crystal X-ray data of the mixed layer compound La32Nb28S88 reported by Meerschaut, Rabu & Rouxel [Jr. Solid State Chem. (1989), 78, 35-45] in an orthorhombic supercell, a=23.216, b = 5.806, c= 23.031 ,A,, space group Bbcb, were analyzed in terms of a composite crystal (LaS)~.~4NbS2, consisting of an LaS part with a=5. 325with Nb in trigonal prisms of S atoms (as in 2H-NbS2). NbS2 sandwiches lc apart are displaced with respect to each other by over ½b. The composition of the compounds is determined by the ratio a/a" and the number of formula units per unit cell of the two sublattices. The symmetry of the complete structure, including the effect of the mutual modulation, is analyzed in terms of a four-dimensional superspace group.

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