Acta Cryst. (2009). E65, i20  [ doi:10.1107/S1600536809005455 ]

C-type Nd₂Se₃

C. Schneck, P. Höss and T. Schleid

Abstract: The title compound, neodymium sesquiselenide, is isotypic with the other known rare-earth metal(III) selenides M₂Se₃ (M = La-Pr and Sm-Lu) with the cubic C-type structure. It adopts a cation-defective Th₃P₄-type arrangement with close to 8/9 of the unique neodymium-cation site occupied, leading to the composition Nd_2.667Se₄ (Z = 4) or Nd₂Se₃ (Z = 5.333), respectively. The Nd³⁺ cations are thus surrounded by eight selenide anions, forming trigonal [NdSe₈]^13- dodecahedra, whereas the Se^2- anions exhibit a sixfold coordination, but due to the under-occupation of neodymium, each one is statistically surrounded by only 5.333 cations. The crystal studied was a merohedral twin with a 0.31 (6):0.69 (6) domain ratio.

Online 21 February 2009

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