To What Extent Does the Zintl-Klemm Formalism Work? The Eu(Zn1-xGex)(2) Series

TitleTo What Extent Does the Zintl-Klemm Formalism Work? The Eu(Zn1-xGex)(2) Series
Publication TypeJournal Article
Year of Publication2009
AuthorsYou TS, Lidin S, Gourdon O, Wu YQ, Miller GJ
Journal TitleInorganic Chemistry
Date PublishedJul 20
ISBN Number0020-1669
Accession NumberISI:000268137900016
Keywordsalb2-type structure, ba, behavior, ca, intermetallic compounds, la3in5, phases, sr, superconductivity, ternary silicides

The series of ternary polar intermetallics Eu(Zn1-xGex)(2) (0 <= x <= 1) has been investigated and characterized by powder and single-crystal X-ray diffraction as well as physical property measurements. For 0.50(2) <= x < 0.75(2), this series shows a homogeneity width of hexagonal AIB(2)-type phases space group P6/mmm, Pearson symbol hP3) with Zn and Ge atoms statistically distributed in the planar polyanionic 6(3) nets. As the Ge content increases in this range, a decreases from 4.3631(6) angstrom to 4.2358(6) angstrom, while c increases from 4.3014(9) angstrom to 4.5759(9) angstrom, resulting in an increasing c/a ratio. Furthermore, the Zn-Ge bond distance in the hexagonal net drops from 2.5190(3) angstrom to 2.4455(3) angstrom, while the anisotropy of the displacement ellipsoids significantly increases along the c direction. For x < 0.50 and x > 0.75, respectively, orthorhombic KHg2-type and trigonal EuGe2-type phases occur as a second phase in mixtures with an AIB(2)-type phase, Diffraction of the x = 0.75(2) sample shows incommensurate modulation along the c direction; a structural model in super space group P31(00 gamma)00s reveals puckered 6(3) nets. Temperature-dependent magnetic susceptibility measurements for two AIB(2)-type compounds show Curie-Weiss behavior above 40.0(2) K and 45.5(2) K with magnetic moments of 7.98(1)mu(B) for Eu(Zn0.48Ge0.52(2))(2) and 7.96(1)mu(B) for Eu(Zn0.30Ge0.70(2))(2), respectively, indicating a (4f)(7) electronic configuration for Eu atoms (Eu2+). The Zintl-Klemm formalism accounts for the lower limit of Ge content in the AIB(2)-type phases but does not identify the observed upper limit. In a companion paper, the intrinsic relationships among chemical structures, compositions, and electronic structures are analyzed by electronic structure calculations.

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