TOPAS Workshop 2019
The TOPAS Workshop 2019 will be a hands-on session on the analysis software TOPAS, which is one of the most powerful programs in order to analyze powder diffraction and total scattering data. TOPAS can be used for the indexing of powder diffractograms, for the application of crystal structure solution algorithms and finally to perform Rietveld refinements on the data. Its least squares refinement routine and handling is superior compared to other software packages in the field like Fullprof or GSAS. Moreover the embedded macro language allows for the flexible integration of own ideas like fitting equations or even new types of mathematical/crystallographic restraints and constraints in order to model powder diffraction data accurately. Furthermore TOPAS can handle hundreds or thousands of data sets simultaneously, which is beneficial for the analysis of powder diffraction data collected in situ on laboratory machines as well as at neutron and/or synchrotron beamlines.
It is the aim of this intensive course to impart the basics of the TOPAS software and the Rietveld method in theory and practice. Using selected examples the entire process from profile fitting using fundamental parameters towards crystal structure determination and refinement will be explained. In particular the following topics will be covered:
- Basics of powder diffraction and Rietveld Refinement
- Whole Powder Pattern-Fitting (WPPF), fundamental parameters (FP), complex reflection profiles
- Determination of the Instrument Resolution Function (IRF) for powder diffractometers
- Angular and intensity corrections (LP-Faktor, absorption, microabsorption, extinction, preferred orientation, sample height, zero error, …)
- Methods to develop a starting model for crystal structure determination
- Penalty-functions, constraints, restraints
- Rigid Bodies (RB) (flexible polyhedra, molecules, z-matrices)
- Strategies for structure determination, global optimization in direct space, Charge-Flipping (CF)
- Difference-Fourier-analysis in combination with Rietveld refinement
- Isotropic and anisotropic microstructural parameters
- Quantitative Phase Analysis (QPA) with the Rietveld method
- Different methods for quantifying the amorphous content
- Symmetry and rotation modes as alternatives ways of describing crystal structures
- Parametric Rietveld refinements (includes basic macro-programming)
- Local and global optimization of stacking faulted superstructures
- Local and global optimization of the Pair-Distribution-Function (PDF)
- The making of Rietveld-Plots for publications
- Prof. Dr. rer. nat. habil. Robert E. Dinnebier, Max Planck Institute for Solid State Research, Stuttgart Germany
- Dr. Martin Etter, Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany
The workshop is intended for Master and PhD students as well as Postdoctoral Researchers. The workshop will be limited to a maximum of 25 participants.
Participants must bring their own laptops with Windows 10 installed (Laptops with Linux or MacOS or virtual machines running Windows will not be supported by the organizers!). For the workshop, temporarily, a commercial Bruker TOPAS version will be used. Due to this reason, the laptops must possess a functional WiFi connection, since the software licenses are distributed via WiFi.
The workshop is free of charge.
For further questions, please contact Dr. Martin Etter: email@example.com