Yb_9+xCuMg_4–x (x = 0.034): A <i>κ</i>-Phase Formed by Lanthanoids

Author(s)

Serena De Negri, Vitaliy Romaka, Paulo Solokha, Adriana Saccone, Gerald Giester, Herwig Michor, Peter F. Rogl

Abstract

Atom order in the crystal structures of Yb

₂Cu

_2-xMg (x = 0.17; Mo

₂FeB

₂-type; P4/mbm; a = 0.75592(2) nm; c = 0.40282(1) nm) and Yb

_9+xCuMg

_4-x (x = 0.034; Hf

₉Mo

₄B-type; P6

₃/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, Yb

_9+xCuMg

_4-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 Yb

₆-octahedra, which encompass Yb

₆Mg

₆-icosahedra (filled by a mix of Mg/Yb atoms) and Yb

₆-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 Yb

₉Mg

₄ 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 Yb

₉CuMg

₄ 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 (

¹S

₀) 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

_D = 140 K as typical for soft materials.

Organisation(s)

Department of Mineralogy and Crystallography, Department of Materials Chemistry

External organisation(s)

Università degli Studi di Genova, Lviv Polytechnic National University, Technische Universität Wien

Journal

Inorganic Chemistry

Volume

55

Pages

8174-8183

No. of pages

10

ISSN

0020-1669

DOI

https://doi.org/10.1021/acs.inorgchem.6b01315

Publication date

07-2016

Peer reviewed

Yes

Austrian Fields of Science 2012

104003 Inorganic chemistry, 104017 Physical chemistry, 104011 Materials chemistry, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Inorganic Chemistry, Physical and Theoretical Chemistry

Portal url

https://ucris.univie.ac.at/portal/en/publications/yb9xcumg4x-x--0034-a-phase-formed-by-lanthanoids(5f1c1ca0-3fe3-46b5-b828-8c544f44b71e).html