Results and conclusions of the internet based “Search/match round robin 2002”

Abstract

To test the effectiveness of phase identification software, a two-stage search/match round robin using powder X-ray diffraction data was organized, through the internet and world wide web. The first stage provided powder patterns and a vague sample origin, the second stage provided the chemistry and sample history. While the statistics are not robust, it shows that routine phase identification without chemistry can be performed, providing effective modern third generation search/match software is used; the most up to date databases are available; and well trained, experienced scientists perform the analysis.

Clean and Efficient Synthesis Using Mechanochemistry: Coordination Polymers, Metal-Organic Frameworks and Metallodrugs

“…The quantitative reaction yields also facilitated the structural characterization of mechanochemical products using powder X-ray diffraction data, leading to the structural characterization of bismuth disalicylate monohydrate, an outstanding target from the 2002 Second Structure Determination by Powder Diffractometry Round Robin challenge (SDPDRR-2). 79 The crystal structure revealed a two-dimensional hybrid inorganic-organic material and corrected the previously proposed composition 80 involving hydroxide ligands (Figure 10b). The structure of bismuth disalicylate hydrate is currently the only known crystal structure for a bismuth salicylate complex without auxiliary organic ligands.…”

Phase Identification and Quantitative Methods

“…Owing to the (cos θ) dependence, this range is insufficient to easily separate zero-point error from sample displacement, so both errors can often be lumped together as one or the other. Modern search-match software is not as sensitive to systematic errors as some of the older algorithms, and can handle significant displacements (Le Meins et al, 2003). Should it be deemed necessary, options available to determine and correct the errors are to use an internal standard, or possibly cell-parameter refinement.…”

“…Different algorithms have been developed to improve the speed and reliability of the search-match process. Search-match is so central to diffraction analysis that a Round Robin was undertaken to compare software and the contribution of user skill to the process (Le Meins et al, 2003).…”

Frontiers between crystal structure prediction and determination by powder diffractometry

“…Predicted crystal structures need to be confirmed, and this has to be done before the structure determination, if one expects any benefit from the efforts expended. The next step was thus to calculate the corresponding powder patterns and to test the feasibility of search-match identification procedures [latest round robin results in Le Meins et al (2003)], allowing for some kind of “immediate structure solution,” even before indexing, which is discussed here.…”