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Synthesis and Modulated Crystal Structure of KBaNbS 4
Author(s) -
Wu Yuandong,
Doert Thomas,
Bensch Wolfgang
Publication year - 2005
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200500255
Subject(s) - superspace , crystal structure , crystallography , substructure , lattice (music) , ion , diffraction , libration (molecule) , chemistry , metal , modulation (music) , tetrahedron , group (periodic table) , materials science , physics , geometry , optics , mathematics , point (geometry) , structural engineering , organic chemistry , supersymmetry , acoustics , engineering , mathematical physics
Single crystals of KBaNbS 4 have been prepared by the reaction of Nb with an in situ formed melt of K 2 S 3 , BaS, and S at 500 °C. Satellite reflections observed in X‐ray diffraction experiments of these crystals indicate the presence of a one‐dimensional lattice distortion. The modulated structure has been solved and refined from X‐ray data using the superspace group approach. KBaNbS 4 can be described in the (3 + 1)‐dimensional superspace group Pnma (α00)0 s 0 with lattice parameters a = 9.187(1), b = 7.001(1), and c = 12.494(1) Å and a modulation vector q = (0, 0.629(1), 0). In the structure the NbS 4 tetrahedra are stacked along the a axis and show a slight tilting against each other. The K + and Ba 2+ ions follow this tilting, both are slightly shifted from their positions in the average structure. The modulation does not lead to a significant change in the coordination spheres of the metal atoms. The small effects of the modulation correspond to the relatively weak intensities of the satellite reflections. Results of temperature dependent X‐ray investigations indicate that K + librates at higher temperatures and the surrounding S 2− anions follow this motion. With decreasing temperature the libration of K + is reduced and the coordination geometry freezes under formation of an incommensurate modulation. The heavier Ba and Nb atoms are also affected by positional modulation of the substructure and accommodate to their environment.