title: Positional flexibility: syntheses and characterization of six uranium chalcogenides related to the 2H hexagonal perovskite family.
abstract: Six new uranium chalcogenides, Ba4USe6, Ba3FeUSe6, Ba3MnUSe6, Ba3MnUS6, Ba3.3Rb0.7US6, and Ba3.2K0.8US6, related to the 2H hexagonal perovskite family have been synthesized by solid-state methods at 1173 K. These isostructural compounds crystallize in the K4CdCl6 structure type in space group D3d6–R3̅c of the trigonal system with six formula units per cell. This structure type is remarkably flexible. The structures of Ba3FeUSe6, Ba3MnUSe6, and Ba3MnUS6 consist of infinite ∞1[MUQ66–] chains (M = Fe or Mn; Q = S or Se) oriented along the c axis that are separated by Ba atoms. These chains are composed of alternating M-centered octahedra and U-centered trigonal prisms sharing triangular faces; in contrast, in the structures of Ba4USe6, Ba3.3Rb0.7US6, and Ba3.2K0.8US6, there are U-centered octahedra alternating with Ba-, Rb-, or K-centered trigonal prisms. Moreover, the Ba4USe6, Ba3FeUSe6, Ba3MnUSe6, and Ba3MnUS6 compounds contain U4+, whereas Ba3.3Rb0.7US6 and Ba3.2K0.8US6 are mixed U4+/5+ compounds. Resistivity and μ-Raman spectroscopic measurements and DFT calculations provide additional insight into these interesting subtle structural variations.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Adel
authors.initials: A
authors.lastname: Mesbah
authors.forename: Jai
authors.initials: J
authors.lastname: Prakash
authors.forename: Jessica C
authors.initials: JC
authors.lastname: Beard
authors.forename: Eric A
authors.initials: EA
authors.lastname: Pozzi
authors.forename: Mariya S
authors.initials: MS
authors.lastname: Tarasenko
authors.forename: Sébastien
authors.initials: S
authors.lastname: Lebègue
authors.forename: Christos D
authors.initials: CD
authors.lastname: Malliakas
authors.forename: Richard P
authors.initials: RP
authors.lastname: Van Duyne
authors.forename: James A
authors.initials: JA
authors.lastname: Ibers