Acta Crystallographica Section B

Structural Science

Volume 61, Part 4 (August 2005)


research papers



Acta Cryst. (2005). B61, 435-442    [ doi:10.1107/S0108768105015004 ]

Powder diffraction crystal structure analysis using derivative difference minimization: example of the potassium salt of 1-(tetrazol-5-yl)-2-nitroguanidine

L. A. Solovyov, A. M. Astachov, M. S. Molokeev and A. D. Vasiliev

Abstract: The crystal structure of the potassium salt of 1-(tetrazol-5-yl)-2-nitroguanidine [K(C2H3N8O2)] was solved and refined from X-ray powder diffraction data by applying the derivative difference minimization (DDM) method. The compound is of interest as an energetic substance. The structure model was found from a Patterson search. The reflection intensities for the Patterson synthesis were derived from the powder profile by applying a newly developed DDM-based profile decomposition procedure. The use of the DDM method allowed successful location and unconstrained refinement of all the atomic positions, including those of three independent H atoms. The advantages of DDM in terms of the precision and reproducibility of the structural parameters are discussed in comparison to Rietveld refinement results. The failure to refine the H-atom positions by the Rietveld method was attributed to systematic errors associated with the background modelling, which are avoided by DDM.

Keywords: powder diffraction; crystal structure analysis; derivative difference minimization.


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XRD data for A


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Atomic coordinates obtained by DDM


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XRD data for B


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