Exploratory Syntheses and Structures of SrAu4.3In1.7 and CaAg3.5In1.9: Electron-Poor Intermetallics with Diversified Polyanionic Frameworks That Are Derived

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• 作者：Qisheng Lin ; John D. Corbett
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：November 7, 2011
• 年：2011
• 卷：50
• 期：21
• 页码：11091-11098
• 全文大小：989K
• 年卷期：v.50,no.21(November 7, 2011)
• ISSN：1520-510X

文摘

The phase regions around quasicrystals and approximants (QC/ACs) are rich pools for electron-poor intermetallics with novel, complex structures, and bonding patterns. The present SrAu_4.30(1)In_1.70(1) (1) and CaAg_3.54(1)In_1.88(1) (2) were synthesized through chemical tunings of the model CaAu₄In₂ (YCd₆-Type) AC. Single crystal X-ray diffraction analyses reveals that crystal 1 has Pnma (CeCu₆-type) symmetry, with a = 9.102(1) 脜, b = 5.6379(9) 脜, and c = 11.515(2) 脜. The building block in 1 is a 19-vertex cluster Sr@Au₉In₄M₆ (M = Au/In), which vividly mimics Ca@(Au,In)₁₈ in Ca₃Au_12.4In_6.1 (YCd₆-type) in geometry. These clusters aggregate into one-dimensional columns extending along the b axis. Crystal 2 (P6/mmm, a = 20.660(3) 脜, c = 9.410(2) 脜) is closely related to Na₂₆Cd₁₄₁ (hP167) and Y₁₃Pd₄₀Sn₃₁ (hP168), which are differentiated by the selective occupation of Wyckoff 1a (0 0 0) or 2d (1/3 2/3 1/2) sites by Cd or Pd. Crystal 2 adopts the Na₂₆Cd₁₄₁ structure, but the 1a site is split into two partially occupied sites. The synergistic disorder in the hexagonal tunnels along c is a major property. The valence electron count per atom (e/a) values for 1 and 2 are 1.63 and 1.74, respectively, the lowest among any other ternary phases in each system. These values are close to those of ACs in the Ca鈥揂u鈥揗 (M = Ga, In) systems. Electronic structures for both are discussed in terms of the results of TB-LMTO-ASA calculations.