Workshop on Errors, Pitfalls and Problems in Single-Crystal Structure Analysis
Kiel, Germany, July 2012
Single-crystal X-ray diffraction is a routine method used by an increasing number of young scientists who have limited formal training. Unfortunately, sometimes problems occur that lead to incorrect structure determinations, some of which get published. Even if a structure seems to be successfully determined, errors might have occurred which are difficult to detect. These problems were addressed at the 10th Kiel Workshop. The workshop was organized by Christian Näther (Inst. of Inorganic Chemistry, Kiel) and Michael Bolte (Inst. of Inorganic Chemistry, Goethe-U., Frankfurt) as a shared activity of the German Crystallographic Assn (DGK) and the German Chemical Society (GDCh). This course was given in German and was intended for people who already had some practical experience with structure determination.
The workshops addressed problems in five areas: determination of the crystal system, the Laue symmetry and space group; structure solution; structure refinement; twinning; treatment of disordered hydrogen atoms and assessment of the quality of a structure determination. For each topic, an introductory lecture was held and the participants had to tackle structural problems with well-prepared data sets using standard software as described in the workshop manual. This included refinement: in an incorrect space group, in too small and too large unit cells, of sub- and super-structures, of twinned crystals, and using incorrect chemical elements. The organizers believe that people can only resolve problems if they are confronted with them. All solutions were discussed with the whole group.
Assessment by the participants afterwards was unequivocally positive. Students apply half a year before the course begins, even if it is not announced. We have learned that some old structures have been solved with the knowledge acquired in the course.Christian Näther and Michael Bolte