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To What Extent Does the Zintl−Klemm Formalism Work? The Eu(Zn1−xGex)2 Series
Inorganic Chemistry
  • Tae-Soo You, Iowa State University
  • Sven Lidin, Stockholm University
  • Olivier Gourdon, Oak Ridge National Laboratory
  • Yaqiao Wu, Iowa State University
  • Gordon J. Miller, Iowa State University
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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 AlB2-type phases (space group P6/mmm, Pearson symbol hP3) with Zn and Ge atoms statistically distributed in the planar polyanionic 63 nets. As the Ge content increases in this range, a decreases from 4.3631(6) Å to 4.2358(6) Å, while c increases from 4.3014(9) Å to 4.5759(9) Å, resulting in an increasing c/a ratio. Furthermore, the Zn−Ge bond distance in the hexagonal net drops from 2.5190(3) Å to 2.4455(3) Å, 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 AlB2-type phase. Diffraction of the x = 0.75(2) sample shows incommensurate modulation along the c direction; a structural model in super space group P3m̅1(00γ)00s reveals puckered 63 nets. Temperature-dependent magnetic susceptibility measurements for two AlB2-type compounds show Curie−Weiss behavior above 40.0(2) K and 45.5(2) K with magnetic moments of 7.98(1) μB for Eu(Zn0.48Ge0.52(2))2 and 7.96(1) μB 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 AlB2-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.

Reprinted (adapted) with permission from Inorg. Chem., 2009, 48 (14), pp 6380–6390. Copyright 2009 American Chemical Society.

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Tae-Soo You, Sven Lidin, Olivier Gourdon, Yaqiao Wu, et al.. "To What Extent Does the Zintl−Klemm Formalism Work? The Eu(Zn1−xGex)2 Series" Inorganic Chemistry Vol. 48 Iss. 14 (2009) p. 6380 - 6390
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