Characterization and ab Initio XRPD Structure Determination of a Novel Silicate with Vierer Single Chains: The Crystal Structure of NaYSi2O6
datasetposted on 2005-12-12, 00:00 authored by Daniel M. Többens, Volker Kahlenberg, Reinhard Kaindl
The crystal structure of a sodium yttrium silicate with composition NaYSi2O6 has been determined from laboratory X-ray powder diffraction data by simulated annealing, and has been subsequently refined with the Rietveld technique. The compound is monoclinic with space group P21/c and unit cell parameters of a = 5.40787(2) Å, b = 13.69784(5) Å, c = 7.58431(3) Å, and β = 109.9140(3)° at 23.5 °C (Z = 4). The structure was found to be a single-chain silicate with a chain periodicity of four. The two symmetry dependent [Si4O12] chains in the unit cell are parallel to c. A prominent feature is the strong folding of the crankshaft-like chains within the b,c-plane resulting in intrachain Si−Si−Si angles close to 90°. The coordination of the Y3+ ions by O2- is 7-fold in the form of slightly irregular pentagonal bipyramids, with oxygen atoms from four different chains contributing to the coordination polyhedron. Na+ ions are irregularly coordinated by 10 oxygens from two neighboring chains. No disorder of Na+ and Y3+ between the two nontetrahedral cation sites could be observed. Furthermore, micro-Raman spectra have been obtained from the polycrystalline material.
nontetrahedral cation sitesCrystal Structureunit cell parametersoxygen atomscomposition NaYSi 2 O 6ab Initio XRPD Structure DeterminationRietveld techniquesodium yttrium silicateNaYSi 2 O 6Novel SilicateSi 4 O 12coordination polyhedronpentagonal bipyramidscrystal structureunit cellchain periodicity10 oxygens