title: Syntheses, crystal structures, transport properties, and theoretical studies of five members of the MAn2Q5 family: SrU2S5, BaU2Se5, PbU2S5, BaTh2S5, and BaU2Te5.
abstract: Five compounds of the MAn2Q5 family, namely, SrU2S5, BaU2Se5, PbU2S5, BaTh2S5, and BaU2Te5, have been synthesized by high-temperature solid-state reactions. The crystal structures of these compounds were determined by single-crystal X-ray diffraction studies. SrU2S5, BaU2Se5, PbU2S5, and BaTh2S5 crystallize in the PbU2Se5 structure type in space group C2h(5)–P2(1)/c of the monoclinic system, whereas BaU2Te5 adopts the (NH4)Pb2Br5 structure type in space group D4h(18)–I4/mcm of the tetragonal system. There are no Q–Q bonds in these structures, so the formulas charge balance as M(2+)(An(4+))2(Q(2–))5. The An atoms in the monoclinic structure are seven- or eight-coordinated by Q atoms; the U atoms in the tetragonal structure are eight-coordinated. The M atoms in the monoclinic structure are coordinated to either eight or nine Q atoms, depending on the monoclinic β angle; the M atoms in the tetragonal structure are 10-coordinated. Resistivity studies on single crystals of SrU2S5, BaU2Se5, and PbU2S5 show metallic behavior with resistivities of 0.24, 10, and 3.3 mΩ·cm, respectively, at 298 K. Spin-polarized density functional theory in the generalized gradient approximation applied to the four U compounds suggests that they are ferromagnetic. In each compound, the density of states of one spin channel is found to be finite at the Fermi level, whereas there is a gap in the density of states of the other spin channel; this is characteristic of a half-metal.
authors.affiliation: Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Jai
authors.initials: J
authors.lastname: Prakash
authors.forename: Mariya S
authors.initials: MS
authors.lastname: Tarasenko
authors.forename: Adel
authors.initials: A
authors.lastname: Mesbah
authors.forename: Sébastien
authors.initials: S
authors.lastname: Lebègue
authors.forename: Christos D
authors.initials: CD
authors.lastname: Malliakas
authors.forename: James A
authors.initials: JA
authors.lastname: Ibers