Pyroxene‐type compounds NaM3+Ge2O6, with M = Ga, Mn, Sc and In. Issue 9 (7th August 2014)

• Record Type: Journal Article
• Authors: Redhammer, Günther J.; Tippelt, Gerold
• Is Part Of: Acta crystallographica. Volume 70:Issue 9(2014:Sep.)
• Page Start: 852
• Page End: 857
• Publication Date: 2014-08-07
• Subjects: Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229614017768
• Languages: English
• ISSNs: 2053-2296

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The four title compounds, namely sodium gallium germanate, NaGaGe<sub>2</sub>O<sub>6</sub>, sodium manganese vanadate germanate, NaMnV<sub>0.1</sub>Ge<sub>1.9</sub>O<sub>6</sub>, sodium scandium germanate, NaScGe<sub>2</sub>O<sub>6</sub>, and sodium indium germanate, NaInGe<sub>2</sub>O<sub>6</sub>, adopt the high‐temperature structure of the pyroxene‐type chain germanates, with monoclinic symmetry and space group <italic>C</italic>2/<italic>c</italic>. The lattice parameters, the individual and average bond lengths involving <italic>M</italic>1, and the distortion parameters scale well with the ionic radius of the <italic>M</italic>1 cation. NaGaGe<sub>2</sub>O<sub>6</sub> has more distorted <italic>M</italic>1 sites and more extended tetrahedral chains than NaInGe<sub>2</sub>O<sub>6</sub>, in which a high degree of kinking is required to maintain the connection between the octahedral and tetrahedral building units of the pyroxene structure. An exceptional case is NaMnGe<sub>2</sub>O<sub>6</sub>, in which the strong Jahn–Teller effect of Mn<sup>3+</sup> results in more distorted octahedral sites than expected according to linear extrapolation from the other Na<italic>M</italic><sup>3+</sup>Ge<sub>2</sub>O<sub>6</sub> pyroxenes. In contrast with the literature, minor incorporations of V<sup>5+</sup> in the tetrahedral site and a corresponding reduction of Mn<sup>3+</sup> to Mn<sup>2+</sup> in the octahedral sites in the present sample lower the Jahn–Teller distortion and stabilize the Mn‐bearing pyroxene, even allowing its synthesis at ambient pressure.</p> </abstract>