title: Yb9+xCuMg4-x (x = 0.034): A κ-Phase Formed by Lanthanoids.
abstract: Atom order in the crystal structures of Yb2Cu2-xMg (x = 0.17; Mo2FeB2-type; P4/mbm; a = 0.75592(2) nm; c = 0.40282(1) nm) and Yb9+xCuMg4-x (x = 0.034; Hf9Mo4B-type; P63/mmc; a = 1.0169(5) nm; c = 1.0290(5) nm) was determined from powder and X-ray single-crystal counter data analyses supported by electron probe microanalyses. Among the group of the so-called κ-phases, Yb9+xCuMg4-x is the first representative formed by a lanthanoid element. The structure of this κ-phase can be viewed as a typical network of corner-connected empty Yb6-octahedra, which encompass Yb6Mg6-icosahedra (filled by a mix of Mg/Yb atoms) and Yb6-trigonal prisms centered by Cu atoms to complete the three-dimensional metal framework. From another point of view, the same structure is considered as built from infinite polyicosahedral columns of Yb9Mg4 composition with Cu atoms located in trigonal prismatic interstices, highlighting similarities with other Yb-rich Yb-Cu-Mg phases. Density functional theory (DFT) calculations classify Yb9CuMg4 as a polar intermetallic. Metallic-like behavior is inferred from the Sommerfeld constant, γ = 49.2 mJ/mol·K(2), derived from the electronic density of states, calculated at the Fermi level. DFT integration of the f-density of states indicates almost completely filled f-states, revealing 13.6 and 13.7 electrons in the valence band for Yb1 and Yb2 atoms, respectively, close to the Yb(2+) ground state ((1)S0) for both Yb atoms. Magnetic susceptibility data recorded on the same compound are consistent with a nonmagnetic divalent Yb(2+) state. Temperature-dependent heat capacity data display a metallic behavior characterized by a small Sommerfeld constant γ = 64.8 mJ/mol·K(2) and a rather low Debye temperature ΘD = 140 K as typical for soft materials.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Genova , Via Dodecaneso 31, I-16146 Genova, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: De Negri
authors.affiliation: Department of Materials Science and Engineering, Lviv Polytechnic National University , Ustiyanovycha Str. 5, 79013 Lviv, Ukraine.
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Romaka
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Genova , Via Dodecaneso 31, I-16146 Genova, Italy.
authors.forename: Pavlo
authors.initials: P
authors.lastname: Solokha
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Genova , Via Dodecaneso 31, I-16146 Genova, Italy.
authors.forename: Adriana
authors.initials: A
authors.lastname: Saccone
authors.affiliation: Institute of Mineralogy and Crystallography, University of Vienna , Althanstrasse14, A-1090 Wien, Austria.
authors.forename: Gerald
authors.initials: G
authors.lastname: Giester
authors.affiliation: Institute of Solid State Physics, TU Wien , Wiedner Hauptstraße 8-10, A-1090 Wien, Austria.
authors.forename: Herwig
authors.initials: H
authors.lastname: Michor
authors.affiliation: Institute of Materials Chemistry and Research, University of Vienna , Währingerstraße 42, A-1090 Wien, Austria.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Rogl