Topas is a powerful suite of software written by Alan Coelho for the analysis of powder diffraction data. Bruker ( market the original version of topas which comes with a full graphical user interface. An academic-only version is also available from Alan Coelho (

Topas allows you to:

  • analyse constant wavelength and energy dispersive X-ray data
  • analyse constant wavelength and time of flight neutron data
  • perform Rietveld/Pawley/individual reflection fitting
  • index powder diffraction data
  • solve structures by simulated annealing and charge flipping
  • perform isodisplace distortion mode refinements
  • etc

You can find lots more information about topas on various web sites. Try:

John Evans' site:
Alan Coelho's site:
Bruker's site:

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