Acta Cryst. (2007). E63, i187  [ doi:10.1107/S1600536807048593 ]

Ce₃Mg_0.5GeS₇ from single-crystal data

L. D. Gulay, M. Daszkiewicz, M. R. Huch and A. Pietraszko

Abstract: Single crystals of tricerium hemimagnesium germanium heptasulfide were obtained by sintering a Ce₂S₃-MgS-GeS₂ mixture. The compound crystallizes in the space group P6₃ and is isotypic with other Ln₃T_0.5XS₇ phases (Ln = lanthanide, T = divalent transition metal, and X = Si or Ge). The slightly distorted trigonal [MgS₆] antiprism has 3 symmetry, with the Mg position half-occupied. The latter position correlates well with the disordered Ag2 positions in the Ln₃Ag_1-SnS₇ (Ln = La, Ce; = 0.18-0.19) and Ln₃Ag_1-SiS₇ (Ln = La-Nd, Sm; = 0.10-0.23) structures. The present single-crystal study confirms the previous refinement from powder data, but with all displacement parameters refined anisotropically.

Online 10 October 2007

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