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Zintl Phases K4–xNaxSi4(1 ≤ x ≤ 2.2) and K7NaSi8: Synthesis, Crystal Structures, and Solid-State NMR Spectroscopic Investigations

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Scherf, LM 
Pecher, O 
Griffith, KJ 
Haarmann, F 
Grey, CP 


jats:pThe Zintl phases Kjats:sub4–jats:italicx</jats:italic></jats:sub>Najats:italicjats:subx</jats:sub></jats:italic>Sijats:sub4</jats:sub> (1 ≤ jats:italicx</jats:italic> ≤ 2.2) and Kjats:sub7</jats:sub>NaSijats:sub8</jats:sub> are the first representatives of the K–Na–Si system, and both contain tetrahedral [Sijats:sub4</jats:sub>]jats:sup4–</jats:sup> clusters and a charge‐balancing number of Kjats:sup+</jats:sup> and Najats:sup+</jats:sup> cations. All phases of Kjats:sub4–jats:italicx</jats:italic></jats:sub>Najats:italicjats:subx</jats:sub></jats:italic>Sijats:sub4</jats:sub> (1 ≤ jats:italicx</jats:italic> ≤ 2.2) crystallize in a new structure type with space group jats:italicP</jats:italic>2jats:sub1</jats:sub>/jats:italicn</jats:italic>, as determined by single‐crystal X‐ray diffraction analysis of the parent phase Kjats:sub3</jats:sub>NaSijats:sub4</jats:sub>. Rietveld refinement of the X‐ray diffraction data showed that the solid solutions follow Vegard's rule. Kjats:sub7</jats:sub>NaSijats:sub8</jats:sub> can only be synthesized by diffusion‐controlled reaction of binary precursors and is isostructural with known jats:italicA</jats:italic>jats:sub7</jats:sub>jats:italicA′T</jats:italic>jats:sub8</jats:sub> (jats:italicA</jats:italic> = Na–Cs; jats:italicA′</jats:italic> = Li, Na; jats:italicT</jats:italic> = 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 Kjats:sub7</jats:sub>NaSijats:sub8</jats:sub>, which is additionally compared with the related phases jats:italicA</jats:italic>jats:sub7</jats:sub>NaSijats:sub8</jats:sub> (jats:italicA</jats:italic> = Rb, Cs).</jats:p>



Alkali metals Silicon, Zintl phases, NMR spectroscopy, Density functional calculations

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European Journal of Inorganic Chemistry

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European Commission (655444)
We gratefully acknowledge fruitful discussions with Dr. Rachel N. Kerber (Cambridge). L. M. S. is grateful for financial support by the Fonds der Chemischen Industrie and a fellowship from the Studienstiftung des deutschen Volkes. This work was performed using the Darwin Supercomputer of the University of Cambridge High Performance Computing Service (, provided by Dell Inc. using Strategic Research Infrastructure Funding from the Higher Education Funding Council for England and funding from the Science and Technology Facilities Council. K. J. G. thanks the Winston Churchill Foundation of the United States and the Herchel Smith Scholarship for financial support.