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Pyroxene‐type compounds Na M 3+ Ge 2 O 6 , with M = Ga, Mn, Sc and In
Author(s) -
Redhammer Günther J.,
Tippelt Gerold
Publication year - 2014
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229614017768
Subject(s) - germanate , octahedron , ionic radius , crystallography , pyroxene , chemistry , bond length , inorganic chemistry , crystal structure , ion , mineralogy , olivine , organic chemistry
The four title compounds, namely sodium gallium germanate, NaGaGe 2 O 6 , sodium manganese vanadate germanate, NaMnV 0.1 Ge 1.9 O 6 , sodium scandium germanate, NaScGe 2 O 6 , and sodium indium germanate, NaInGe 2 O 6 , adopt the high‐temperature structure of the pyroxene‐type chain germanates, with monoclinic symmetry and space group C 2/ c . The lattice parameters, the individual and average bond lengths involving M 1, and the distortion parameters scale well with the ionic radius of the M 1 cation. NaGaGe 2 O 6 has more distorted M 1 sites and more extended tetrahedral chains than NaInGe 2 O 6 , 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 2 O 6 , in which the strong Jahn–Teller effect of Mn 3+ results in more distorted octahedral sites than expected according to linear extrapolation from the other Na M 3+ Ge 2 O 6 pyroxenes. In contrast with the literature, minor incorporations of V 5+ in the tetrahedral site and a corresponding reduction of Mn 3+ to Mn 2+ 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.