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Incommensurately modulated phase of Rb2CoBr4 at 295 and 200 K
Friese1, Madariaga, Breczewski
1Departamento de Fisica de la Materia Condensada, Universidad del Pais Vasco, Bilbao, Spain.
Acta Crystallographica. Section B, Structural Science
|March 29, 2000
Summary
The crystal structure of Rubidium cobalt bromide (Rb2CoBr4) was determined at room and low temperatures. This inorganic crystal exhibits an incommensurately modulated structure, similar to related compounds.
Area of Science:
- Solid State Chemistry
- Crystallography
- Materials Science
Background:
- Understanding the structural properties of inorganic halide salts is crucial for developing new materials.
- Rubidium cobalt bromide (Rb2CoBr4) is a member of a family of compounds known to exhibit complex structural phases.
Purpose of the Study:
- To determine the crystal structure of Rb2CoBr4 at different temperatures (295 K and 200 K).
- To investigate the nature of its modulated structure and compare it with related compounds like Rb2ZnBr4.
Main Methods:
- X-ray diffraction analysis was performed on Rb2CoBr4 crystals.
- The average crystal structure was refined at room temperature (295 K) in space group Pnam.
- The incommensurately modulated structure was refined at 200 K using superspace group P:Pnam:1ss, including main and satellite reflections.
Main Results:
- At 295 K, Rb2CoBr4 was refined in the average structure Pnam with specific lattice parameters.
- At 200 K, Rb2CoBr4 exhibits an incommensurately modulated structure with a wavevector q = (1/3 + delta)a*.
- The modulation function, amplitudes, phases, and bond distances show similarities to the incommensurately modulated phase of Rb2ZnBr4.
Conclusions:
- Rb2CoBr4 displays an incommensurately modulated structure at low temperatures, indicating complex structural behavior.
- The structural characteristics of Rb2CoBr4 are comparable to those of Rb2ZnBr4, suggesting common underlying principles in this class of materials.