11. May 2018

Featured laboratory: MPI for Solid State Research

The many faces of powder X-ray diffraction

 

As Robert Dinnebier opens the door of the X-ray facility of the Max Planck Institute for Solid State Research in Stuttgart, Germany, a smile comes almost automatically. Nine powder diffractometers are running, each optimized for a specific analysis. “We have many interests and many collaborations”, comments Dinnebier, “and we do not compromise on data quality, not even when we do a standard material screening.” Indeed, the group’s interest in determining the long- and short-range structure of condensed matter keeps the instruments occupied, instrument developers motivated, and publishers busy. Namely, the average yield of the lab is 23 publications per year, mostly in high-impact journals. This is even more impressive if one takes the size of the group into account. There are only Dinnebier, an engineer, a technician, two postdocs and two PhD students.

 

The Dinnebier group at the MPI for Solid State Research in Stuttgart, Germany: Professor Robert Dinnebier, Christine Stefani, Frank Adams, Gianpiero Gallo, Dr. Sebastian Bette, Luzia Germann and Dr. Maxwell Terban (clockwise from top).

 

The main focus of Sebastian Bette, one of the postdocs, is the corrosion of heritage objects. Corrosion of products is usually considered unwanted or negative, but Bette is causing it on purpose. Namely, production of pigments using corrosion has been known since antiquity, but the processes and products were poorly understood. Bette is changing that [1,2]. “Some processes are very slow and require long experiments”, comments Bette. “Collecting data in the lab is the only option. We are very happy with our setup!”

 

The setup for in situ PXRD features a Debye-Scherrer geometry, three simultaneously operating MYTHEN2 1K detectors and various attachments for controlling temperature and humidity. As analysis of the data from the frequently semi- or non-crystalline samples is by no means easy, Bette is increasingly interested in Pair Distribution Function (PDF) analysis [3,4]. With the arrival of a new postdoc, his PDF research has got new momentum.

 

Sebastian Bette (left) and Max Terban in front of their diffractometer.

 

Maxwell Terban, now the resident PDF expert in the lab, mastered his skills in the Billinge group, at Columbia University in New York City. “PDF is a technique complementary to PXRD. To promote it as a standard technique for material characterization, the data need to be collected in a laboratory, and preferably fast”, says Terban. As PDF measurements in a laboratory may take more than a day, the first step was to optimize the instrument. The group decided on a custom-made STOE STADI P, with an Ag source. Each of three simultaneously operating MYTHEN2 1K detectors features a modified housing that helps minimize air scatter (see image below). “This setup allows Qmax of 18 Å to be collected in two shots. Our aim is to reduce the measurement time to one hour, and use the data for routine verification of the local structure”, comments Terban, “Sebastian and I will present the details at the EPDIC in Edinburgh!”

 

Custom STOE STADI P diffractometer with a Ag source and three simultaneously operating MYTHEN2 1K detectors with housings modified to minimize air scatter.

 

We are definitely looking forward to hearing about the laboratory PDF from Bette and Terban, but this will not be the only contribution from the Dinnebier group. Luzia Germann is still working on her PhD, but she already has a track record of great publications, mostly in the field of mechanochemistry [5,6]. She finds the collaboration with the groups of Ivan Halasz and Tomislav Friščić, two pioneers of solvent-free chemistry, particularly interesting. “For me as a chemist, it is fascinating to see how a reaction is progressing from reactants, intermediates to products, without excessive use of solvents. Powder X-ray diffraction is an excellent tool to monitor these green synthesis processes in situ”, explains Germann.

 

Germann will be finishing her PhD soon, but hers won’t be the last of the successful PhD theses in the lab. A new PhD student, Gianpiero Gallo, joined the group in January, and yet another PhD was recently filled. The winner is not announced yet, but we are detecting a great future for the whole group. Their lab shows remarkable technical capacity: nine diffractometers, four sets of MYTHEN2 multimodular systems, the technician Christine Stefani and the engineer Frank Adams. And the group gives back to the community. All non-experts in the PXRD field should keep an eye on PXRD schools organized by the group or read the new book on Rietveld refinement.

 

Publications

 

  1. Bette et al., Inorg. Chem. (2017), 56, 5762
  2. Bette et al., Nach. Chem. (2017), 65, 1185
  3. Bette et al., Dalton Trans. (2017), 46, 15216
  4. Bette et al., J. Appl. Cryst. (2015), 48, 1706
  5. Haase et al., Mater. Chem. Front. (2017), 1, 1354-1361
  6. Julien et al., J. Am. Chem. Soc. (2016), 138(9), 2929-2932