Crystal structure of low-symmetry rondorfite
- NPO Neokhim (Russian Federation)
- Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)
The crystal structure of an aluminum-rich variety of the mineral rondorfite with the composition Ca{sub 16}[Mg{sub 2}(Si{sub 7}Al)(O{sub 31}OH)]Cl{sub 4} from the skarns of the Verkhne-Chegemskoe plateau (the Kabardino-Balkarian Republic, the Northern Caucasus Region, Russia) was solved in the triclinic space group with the unit-cell parameters a = 15.100(2) A, b = 15.110(2) A, c = 15.092(2) A, {alpha} = 90.06(1) deg., {beta} = 90.01(1) deg., {gamma} = 89.93(1) deg., Z = 4, sp. gr. P1. The structural model consisting of 248 independent atoms was determined by the phase-correction method and refined to R = 3.8% with anisotropic displacement parameters based on all 7156 independent reflections with 7156 F > 3{sigma}(F). The crystal structure is based on pentamers consisting of four Si tetrahedra linked by the central Mg tetrahedron. The structure can formally be refined in the cubic space group (a = 15.105 A, sp. gr. Fd-bar 3, seven independent positions) with anisotropic displacement parameters to R = 2.74% based on 579 reflections with F > 3{sigma}(F) without accounting for more than 1000 observed reflections, which are inconsistent with the cubic symmetry of the crystal structure.
- OSTI ID:
- 21090615
- Journal Information:
- Crystallography Reports, Vol. 53, Issue 2; Other Information: DOI: 10.1007/s11445-008-2006-2; Copyright (c) 2008 Pleiades Publishing, Ltd; Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7745
- Country of Publication:
- United States
- Language:
- English
Similar Records
Calcio-olivine {gamma}-Ca{sub 2}SiO{sub 4}: I. Rietveld refinement of the crystal structure
Crystal structure of larnite {beta}-Ca{sub 2}SiO{sub 4} and specific features of polymorphic transitions in dicalcium orthosilicate