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- Title
Accurate unrestrained DDM refinement of crystal structures from highly distorted and low-resolution powder diffraction data.
- Authors
Solovyov, Leonid A.
- Abstract
The structure of benzene:ethane co-crystal at 90 K is refined with anisotropic displacement parameters without geometric restraints from high-resolution synchrotron X-ray powder diffraction (XRPD) data using the derivative difference method (DDM) with properly chosen weighting schemes. The average C—C bond precision achieved is 0.005 Å and the H-atom positions in ethane are refined independently. A new DDM weighting scheme is introduced that compensates for big distortions of experimental data. The results are compared with density functional theory (DFT) calculations reported by Maynard-Casely et al. [(2016). IUCrJ, 3, 192-199] where a rigid-body Rietveld refinement was also applied to the same dataset due to severe distortions of the powder pattern attributable to experimental peculiarities. For the crystal structure of 2-aminopyridinium fumarate–fumaric acid formerly refined applying 77 geometric restraints by Dong et al. [(2013). Acta Cryst. C69, 896–900], an unrestrained DDM refinement using the same XRPD pattern surprisingly gave two times narrower dispersion of interatomic distances.
- Subjects
CRYSTAL structure; BENZENE; DENSITY functional theory
- Publication
Acta Crystallographica Section B: Structural Science, Crystal Engineering & Materials, 2016, Vol 72, Issue 5, p738
- ISSN
2052-5192
- Publication type
Article
- DOI
10.1107/S2052520616011690