Modulation functions of incommensurately modulated Cr₂P₂O₇ studied by the maximum entropy method (MEM)

Title data

Li, Liang ; Schönleber, Andreas ; van Smaalen, Sander:
Modulation functions of incommensurately modulated Cr₂P₂O₇ studied by the maximum entropy method (MEM).
In: Acta Crystallographica Section B. Vol. 66 (2010) Issue 2 . - pp. 130-140.
ISSN 2052-5206
DOI: https://doi.org/10.1107/S0108768110003393

Official URL:

Abstract in another language

The maximum entropy method (MEM) has been used to determine electron density in superspace of incommensurately modulated chromium pyrophosphate from X-ray diffraction data measured by Palatinus et al. (2006), Acta Cryst. B 62, 556-566. Chromium pyrophosphate, Cr₂P₂O₇, contains ordered regions (83% of the volume) and regions with disorder. Analysis of the MEM density has allowed the determination of the displacive modulation functions within ordered regions. The disordered regions can be described as the alternate occupation of two conformations of the pyrophosphate group and two positions of the chromium atom, with occupational probabilities that depend continuously on the phase of modulation t. A structure model based on the interpretation of the MEM density provides a fit to the diffraction data of the same quality as the model given by Palatinus et al. (2006). The failure to find a model that better fits the data is attributed to the intrinsic inaccuracy of ∼ 0.01 Å for positions derived from the MEM and to the difficulties in constructing an appropriate model for the anharmonic ADPs and their modulation functions from electron densities.

Further data

Item Type:	Article in a journal
Refereed:	Yes
Keywords:	maximum entropy method; incommensurately modulated structures; electron density
Institutions of the University:	Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography Faculties Faculties > Faculty of Mathematics, Physics und Computer Science Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences
Result of work at the UBT:	Yes
DDC Subjects:	500 Science > 530 Physics
Date Deposited:	07 Aug 2015 08:37
Last Modified:	27 Jan 2023 08:26
URI:	https://eref.uni-bayreuth.de/id/eprint/17602