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

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.

X-ray Structural Modeling and Gas Adsorption Analysis of Cagelike SBA-16 Silica Mesophases Prepared in a F127/Butanol/H2O System

“…The calculated and experimental structure factors are compared in Table and the final fits of the calculated to the observed XRD patterns are shown in Figure . The experimental structure factors were derived from the diffraction profiles by applying the DDM decomposition method . While the observed and calculated XRD intensities differed slightly, the density distribution Fourier maps did not reveal additional reproducible structural features which could be interpreted as regular interconnections between the cavities or other details.…”

Improvement of the Kruk−Jaroniec−Sayari Method for Pore Size Analysis of Ordered Silicas with Cylindrical Mesopores

“…[18][19][20] Moreover, the presence of random complementary pores in the walls of ordered mesopores does not affect the XRD structure modeling results, which makes this method extremely useful for an independent pore width evaluation. 19 In this work, the SAXS and XRD analysis of the SBA-15 and MCM-41 mesostructures was done by applying the continuous density function (CDF) technique 18 in combination with the derivative difference minimization (DDM) method 21 of fullprofile refinement. The structure of SBA-15 and MCM-41 was approximated by a simple model of empty pores and continuous walls similar to that described previously 18 for calcined mesoporous silica.…”

Crystal structure determination by combined synchrotronpowder X-ray diffraction and crystal structure prediction: 1 : 1 l-ephedrined-tartrate

“…Correct location of these hydrogen atoms is indispensable to understanding the corresponding bond strengths/motifs and the structure stability. Although a few cases have been reported where hydrogen positions have been located and refined using PXRD data, 46,47 this is still exceptional and, as this work demonstrates, determination of hydrogen positions from PXRD data alone can give incorrect positions. Indeed, as X-ray scattering from hydrogen is very small, it is common practice to exclude hydrogen atoms from structure solutions and to manually add them, with geometrical constraints, during refinement.…”