Novel high-temperature polymorphs of MgBr2 and MnBr2 - limits of powder diffraction for structure determination
Description
High-temperature polymorphs of magnesium bromide and manganese bromide, hexagonal, Ranti 3m, Z = 3.MgBr2, Mr = 184.13, Cu Kα1, λ = 1.54051 A, T = 973 K, a = 3.9152 (7), c = 19.420 (4) A, V = 257.80 (9) A3. MnBr2, Mr = 214.76, neutron radiation, λ = 1.594 (2) A, T = 773 K, a = 3.92240 (2), c = 19.167 (2) A, V = 255.38 (3) A3, Rietveld refinement, 10 ≤ 20 ≤ 1500, Rwp = 0.13. The hitherto unknown high-temperature polymorphs of both MgBr2 and MnBr2 crystallize in the CdCl2 form. The manganese compound is pseudocubic [a = 11.0864 (1) A at 773 K] above 623 K. Distinction between the rhombohedral layered CdCl2 structure and the cubic three-dimensional net λ-MnO2 structure is not possible by powder diffraction experiments alone. Additional observations must be employed. The JCPDS File Nos. for MnBr2 and MgBr2 are 43-1499 and 43-1500 respectively. (orig.)
Additional details
Publishing Information
- Journal Title
- Acta Crystallographica. Section B: Structural Science
- Journal Volume
- 48
- Journal Issue
- 6
- Journal Page Range
- p. 761-763.
- ISSN
- 0108-7681
- CODEN
- ASBSDK
INIS
- Country of Publication
- Denmark
- Country of Input or Organization
- Denmark
- INIS RN
- 24032409
- Subject category
- S36: MATERIALS SCIENCE;
- Descriptors DEI
- CRYSTAL STRUCTURE; CUBIC LATTICES; HEXAGONAL LATTICES; LATTICE PARAMETERS; MAGNESIUM BROMIDES; MANGANESE BROMIDES; NEUTRON DIFFRACTION; POWDERS; SPACE GROUPS; TEMPERATURE RANGE 0400-1000 K; X-RAY DIFFRACTION
- Descriptors DEC
- ALKALINE EARTH METAL COMPOUNDS; BROMIDES; BROMINE COMPOUNDS; COHERENT SCATTERING; CRYSTAL LATTICES; DIFFRACTION; HALIDES; HALOGEN COMPOUNDS; MAGNESIUM COMPOUNDS; MANGANESE COMPOUNDS; MANGANESE HALIDES; SCATTERING; SYMMETRY GROUPS; TEMPERATURE RANGE; TRANSITION ELEMENT COMPOUNDS
Optional Information
- Notes
- Complete Structure Data may be found in ICSD file.