Dr. Thomas Weber (D-MATL X-Ray Service Platform)
The D-MATL X-ray platform supports D-MATL members (and also external users) with problems that can be solved with X-ray diffraction methods or, more generally, with any problems that are related to crystallography. For an overview about the available infrastructure and services provided see www.xray.mat.ethz.ch. Most of the service requests concern standard problems that require limited user support for data collection or evaluation. However, in my presentation I will talk about two long-term research projects I did together with D-MATL groups. The first is a collaboration with the Spaldin group about the thermoelectric compound PbTe, which has some interesting physical properties. By combining ab-initio molecular dynamics simulation methods and experimental information from X-ray diffuse scattering we succeeded in resolving a controversial discussion in literature about the structural origin of the physical effects. The second part of my presentation will address a joint project with the Schlüter group regarding the structural characterisation of two-dimensional polymers. In the single-crystal-to-single-crystal polymerisation approach it is straightforward to monitor the average conversion from the monomer to the polymer. However, standard methods do not allow the identification of the local polymerisation mechanisms, e.g. how polymerisation propagates through the crystal and which structural properties are crucial for compensating unavoidable local strain in the intermediate states. Some of these questions could be answered with the help of Bragg and diffuse X-ray scattering.