Zintl Phases K_4-m>xm>Nam>_xm>Si₄ (1 ≤ m>xm> ≤ 2.2) and K₇NaSi₈: Synthesis, Crystal Structures, and Solid-State NMR Spectroscopic Investigations

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• 作者：Lavinia M. Scherf ; Oliver Pecher ; Kent J. Griffith ; Frank Haarmann ; Clare P. Grey and Thomas F. F&auml ; ssler
• 刊名：European Journal of Inorganic Chemistry
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：2016
• 期：28
• 页码：4674-4682
• 全文大小：1162K
• ISSN：1099-0682c

文摘

The Zintl phases K_4–m>xm>Nam>_xm>Si₄ (1 ≤ m>xm> ≤ 2.2) and K₇NaSi₈ are the first representatives of the K–Na–Si system, and both contain tetrahedral [Si₄]^4– clusters and a charge-balancing number of K⁺ and Na⁺ cations. All phases of K_4–m>xm>Nam>_xm>Si₄ (1 ≤ m>xm> ≤ 2.2) crystallize in a new structure type with space group m>Pm>2₁/m>nm>, as determined by single-crystal X-ray diffraction analysis of the parent phase K₃NaSi₄. Rietveld refinement of the X-ray diffraction data showed that the solid solutions follow Vegard's rule. K₇NaSi₈ can only be synthesized by diffusion-controlled reaction of binary precursors and is isostructural with known m>Am>₇m>A′Tm>₈ (m>Am> = Na–Cs; m>A′m> = Li, Na; m>Tm> = Si, Ge) phases. A combination of solid-state NMR investigations and quantum mechanical calculations served to show the anisotropic chemical bonding behavior of all the atoms in K₇NaSi₈, which is additionally compared with the related phases m>Am>₇NaSi₈ (m>Am> = Rb, Cs).