Method found for analyzing complicated, tiny crystals

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Success after ten years of research: Three intergrown compounds discovered

The graph shows in the background a section of the measured data, an X-ray diffr
The graph shows in the background a section of the measured data, an X-ray diffraction pattern of the phosphorus oxide nitrides. In the foreground are sections of the crystal structure. These are networks of...

The atomic structure of solid substances can often be analyzed quickly, easily and very precisely using X-rays. However, this requires that crystals of the corresponding substances are available. Chemist Oliver Oeckler of the University of Leipzig and his team are developing methods to make this possible even for very small crystals that are invisible to the naked eye. These include so-called phosphorus oxide nitrides, which consist of phosphorus, nitrogen and oxygen and do not occur like this in nature. This novel class of compounds, which has been difficult to access until now, is thought to have special properties because of its unusual structures. Oeckler and his team have developed a method that has enabled them, together with Wolfgang Schnick of the Ludwig Maximilian University of Munich, to determine the complicated crystal structure of new phosphorus oxide nitrides in ten years of research. They have just published their findings in the journal -Chemistry - A European Journal-.

In the analysis of the crystal structure, the combination of electron microscopy and synchrotron radiation - intense X-rays generated in a special way at a large-scale research facility - plays a decisive role. However, the analysis of phosphorus oxide nitride shows that this is sometimes not enough. The substance, which could form the basis for novel phosphors in future studies, for example, was produced for the first time back in 2014, but its structure has not yet been elucidated because it was previously considered a class of compounds that was difficult to access.

Daniel Günther, a doctoral student in Oeckler’s research group, has now been able to solve the puzzle together with his mentor. -It wasn’t the data that did it, but a trick of nature. It’s not just one substance, but three very complicated, intertwined compounds," explains Günther, who is the first author of the study.

Sections of the atomic arrangements formed a modular system, so to speak, from which complicated and also disordered structures can emerge. -An investigation of this kind requires extremely conscientious work, for which only a few employees can muster the necessary patience and concentration. Without a research sabbatical and such a dedicated staff, it probably would not have worked. Most people would have been horrified to discard the data, which at first glance appeared to be unanalysable, and would never have mentioned it again," says Oliver Oeckler. It is not only about the structure of oxonitride phosphates, which the researchers consider very interesting, but also about the method of analysis. Using the procedure described in their article, similar analytical problems with completely different substances can also be solved.

Publication in -Chemistry -A European Journal-:
-Modular Principle for Complex Disordered Tetrahedral Frameworks in Quenched High-pressure Phases of Phosphorus Oxide Nitrides" ,

Susann Huster