The (3 + 1)-dimensional superspace description of the commensurately modulated structure of p-chlorobenzamide (α-form) and its relation to the γ-form
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A. Schönleber
Abstract
The room temperature structure (α-form) of the organic compound p-chlorobenzamide, C7H6ClNO, can be described as a classical three-dimensional periodic superstructure (αS) and also as a commensurately modulated structure (αM) in (3 + 1)-dimensional superspace. The diffraction pattern is characterized by a clear difference in intensity between main and satellite reflections. All reflections can be indexed with four indices hklm in a triclinic unit cell and one modulation vector in the superspace group P1̅(αβγ) with the modulation vector q⃗ = 1/3·a⃗*. The structure undergoes a phase transition at higher temperature. In this phase transition the modulation vanishes as indicated by the disappearance of the satellite reflections. The resulting high temperature phase (γ-form) contains one molecule in the asymmetric unit, the space group is P1̅. The high temperature structure (γ) is very close to the reference structure of the modulated model at room temperature. The phase transition can therefore be understood as a loss of the modulation at high temperature.
© 2003 Oldenbourg Wissenschaftsverlag GmbH
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- Books Received
Artikel in diesem Heft
- Preparation and crystal structure of a new high-pressure phase (V0.5Re0.5)O2 with rutile-type structure
- Electron crystallography of zeolites. 1. Projected crystal structures of ZSM-5 and ZSM-11
- The structures of ZrNCl, TiOCl and AlOCl in the light of the Zintl-Klemm concept
- Single crystal neutron diffraction study of the phase transition in (NH4)H5(PO4)2
- The crystal structure of Er(HPO4)(NO3)·3 H2O: ab initio determination from X-ray powder diffraction data
- Molecular and crystal structure of 5-amino-1H-[1,2,4]triazole-3-carboxylic acid derivatives
- Synthesis and structural investigation of (4-methoxy-phenyl)-[4-(4-methoxy-phenyl)-1-(1-phenylethylidene-amino)-2-thioxo-1,2-dihydro-pyrimidin-5-yl]-methanone
- Structural and spectral studies of N-(3-hydroxypyridine-2-yl)salicylideneimine and N-(3-hydroxypyridine-2-yl)-5-bromosalicylideneimine and their dimethyltin(IV) complexes
- Synthesis, crystal structure and electrochemical behaviour of [2,6-bis(3,5-dimethylpyrazolyl)pyridine](dithiocyanato)cobalt(II)
- Crystal structure and properties of L-arginine diphosphate
- The (3 + 1)-dimensional superspace description of the commensurately modulated structure of p-chlorobenzamide (α-form) and its relation to the γ-form
- Books Received
