title: Reticular merohedral twinning within the La9Sb5O5 structure family: structure of Pr9Sb5O5, Sm9Sb5O5 and Dy9Sb5O5.
abstract: The novel antimonide oxides Pr(9)Sb(5)O(5), Sm(9)Sb(5)O(5) and Dy(9)Sb(5)O(5) were synthesized from the respective RESb, the rare-earth metals (RE = Pr, Sm, Dy), and RE(2)O(3) (RE = Sm, Dy) or Pr(4)O(7), respectively, in sealed tantalum ampoules at 1920 K. Those compounds, which are sensitive against air and moisture, form black cube-like crystals with metallic lustre. They crystallize in the La(9)Sb(5)O(5) type of structure, which represents a fivefold superstructure of the KCoO(2) structure: O(10)K(5)Co(5)[sign: see text]La(9)[sign: see text]Sb(5)O(5). The investigated crystals of the Sm and Dy compounds were twinned using the reticular merohedral law, with the twin symmetry 4/mm'm', and the (310) and (120) mirror planes as twinning symmetry elements. The twin index is [j] = 5.
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergtrasse 1, D-70569 Stuttgart, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Nuss
authors.forename: Martin
authors.initials: M
authors.lastname: Jansen