GSAS-II Home

GSAS-II is an open source python project that addresses all types of crystallographic studies, from simple materials through macromolecules, using both powder and single-crystal diffraction with both x-ray and neutron probes. Measurements can be constant wavelength or (in future) neutron TOF. At present, code is being developed for all the various steps in diffraction analysis, such as data reduction, peak analysis, indexing, structure solution and structure refinement. The source code can be found at ​https://subversion.xor.aps.anl.gov/pyGSAS/trunk/

At present GSAS-II can be used for processing of area detector data, peak fitting, auto-indexing, Pawley and Rietveld fitting. Many of the nice features of GSAS are present and some things work much better than in GSAS, but other features are yet to come. At this point only x-rays and constant wavelength neutrons are implemented (no TOF). The GUI is self-documenting with help pages for every GUI page. The code is changing on a regular basis, so expect things to break from time to time and you should 'Update' frequently to stay abrest of new features as they are added.

GSAS-II User Documentation

Help file: ​https://subversion.xor.aps.anl.gov/pyGSAS/trunk/help/gsasII.html

Tutorials (help file may have include new tutorials not listed here)

• ​Starting GSAS-II
• ​Powder pattern peak picking, fitting and indexing
• ​Lab X-ray powder pattern Rietveld refinement
• ​CW Neutron powder pattern Rietveld refinement with constraints
• ​Combined neutron x-ray Rietveld refinement and Fourier maps
• ​2-D Image calibration
• ​2-D Image integration

Installation instructions:

• Windows
• Mac OS X
• Linux

GSAS-II Project tracking

Updates to the source code can be followed using the ​Timeline Trac tool at this website. The Tickets and Roadmap features are not currently in use.

GSAS-II Developer Notes

Miscellaneous Notes for Code Developers

For a complete list of GSAS-II wiki pages, see TitleIndex.