Artigo Revisado por pares

Crystal structures of Ca 5 Ge 3 O 11 and wollastonite-type GaGeO 3

1997; De Gruyter; Volume: 212; Issue: 7 Linguagem: Inglês

10.1524/zkri.1997.212.7.519

ISSN

2196-7105

Tópico(s)

High-pressure geophysics and materials

Resumo

Abstract The crystal structures of triclinic Ca 5 Ge 3 O 11 and triclinic wollastonite-type CaGeO 3 have been determined by X-ray diffraction using single crystals grown from a K 2 MoO 4 flux. Ca 5 Ge 3 O 11 is closely related to monoclinic Ca 5 (Ge,Si) 3 O 11 and crystallizes in the C [unk] space group with the cell parameters: a = 10.855(2) Å, b = 8.715(2) Å, c = 10.998(2) Å, α = 90.60(3)°, β = 96.49(3)°, γ = 90.17(3)°, Z = 4, wR ( F 2 ) = 0.080 for 4877 unique reflections. Ca 5 Ge 3 O 11 is a mixed-anion germanate containing single and double tetrahedra, with a structural formula written as Ca 5 [GeO 4 ] [Ge 2 O 7 ]. CaGeO 3 is isostructural with CaSiO 3 , wollastonite-1T, and crystallizes in the P [unk] space group with the cell parameters: a = 7.269(2) Å, b = 7.526(2) Å, c = 8.094(2) Å, α = 103.44(3)°, β = 94.42(3)°, γ = 90.11(3)°, Z = 6, wR ( F 2 ) = 0.074 for 9279 unique reflections. The CaGeO 3 structure contains tetrahedral dreier single chains corresponding to the structural formula Ca 3 {uB ∞ 1 }[Ge 3 O 9 ]. The bonding in the two compounds is analyzed in terms of a comparison between observed bond valences and bond valences predicted from the bond topology.

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