Abstract
Symmetry reduction in the basic structure of thortveitite-type compound FeInGe2O7–mC22 (C12/m1, No. 12) promoted by the incorporation of yttrium in the formula FeIn1−xYxGe2O7gives rise to a derivative structure called thortveitite-likeAA′Ge2O7–mP44, with symmetry described by the space groupP121/m1 (No. 11) forx= 0.50, 0.75 and 0.90. The structure remains unchanged within the structural type of thortveitite whenx= 0.25. In order to establish structural models for performing a Rietveld refinement to the derivative structure, symmetry relations between space groups connecting the basic and derivative structures were used. The higher contrast to X-rays of Fe3+, In3+and Y3+as well as by the behaviour during the refinements of the isotropic thermal displacements, the values of interatomic distances and calculated bond-valence sums for each atom in the asymmetric unit, were helpful for elucidating the relocation of cations in the different available crystallographic sites generated by the symmetry reduction.
Funder
Consejo Nacional de Ciencia y Tecnología
Publisher
International Union of Crystallography (IUCr)
Subject
Materials Chemistry,Metals and Alloys,Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials