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T. Yamanaka, R. Kurashima, J. Mimaki

X-ray diffraction study of bond character of rutile-type SiO₂, GeO₂ and SnO₂

The charge density and bond character of the rutile-type structures of SiO₂, GeO₂ and SnO₂ were studied by X-ray diffraction using monopole refinement. The refinement of the charge density was performed by least-squares refinement including the Κ-parameter and the electron population in the X-ray atomic scattering parameters. The oxygen′s Κ-parameters of three oxides are 0.91 (SiO₂), 1.06 (GeO₂), 1.14 (SnO₂). The oxygen valence electron of each sample is 1.06(8)e for SiO₂, 1.10(16)e for GeO₂ and 1.13(15)e for SnO₂. These values indicate that the electron distributions are more localized with an increase in the cation atomic number. The difference Fourier map of each sample shows the deformation density of the valence electrons of cations. The overlapping electron orbitals cause the deformation of MO₆ octahedra of rutile-type structures. The ratio between O-O shared and unshared edge and the ratio between the apical and equatorial M-O interatomic distances decrease with the cation ionicity and the repulsive force between the two cations in adjacent octahedra.

Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0044-2968
Volume: 215, 07/2000
Pages: 424

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