Porous Materials

The research focus is on the temperature-dependent interaction between frameworks and templates in simple zeolitic framework compounds such as cancrinites and sodalites. Here, both the framework composition and the pore fillings (template) are systematically varied and the compounds are characterized as a function of temperature. In addition to (temperature-dependent) IR and Raman spectroscopy, thermogravimetry and other methods, (temperature-dependent) Bragg and "total-scattering" diffraction methods with X-rays, synchrotron radiation and neutrons are the main methods of analysis. The aim of the research is to gain a deeper understanding of the temperature-dependent properties of these framework compounds and their formation through the interplay between structural and dynamic aspects of the compounds.

X-ray diffraction (XRD), Rietveld and pair distribution function (PDF)

To model the diffraction data, Rietveld refinements are used in classical Bragg diffraction experiments, and both small-box (PDF-Rietveld) and supercell PDF refinements or reverse Monte Carlo simulations are used in total-scattering diffraction experiments.

Fig: Distribution of iodide in aluminosilicate iodide sodalite determined from total-scattering neutron TOF experiments.

In this context, the development of methods for data analysis and validation is being driven forward. The autocorrelation method (doi.org/10.1515/zkri-2016-2000 ) was further developed for the rapid analysis of large data sets, which makes it possible to determine at which temperatures structural changes become effective without further data manipulation or modeling.

A method for assessing the quality of in-house total-scattering experiments to determine the pair distribution function is currently being developed in this area.

Force fields, DFT

In addition to these experimental methods, simulation methods (force-fields, DFT) are used and also developed (cellular automata: doi.org/10.1016/j.micromeso.2019.109874) .

Research Lead: Lars Robben