Version 26 (modified by toby, 8 years ago) (diff)



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

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.

If you use GSAS-II, please sign up for the GSAS-II mailing list, see web page

Installation instructions

The license for use is here. Also, please sign up for the mailing list after installing GSAS-II.

GSAS-II User Documentation

Help file:

Tutorials (help file may include newer tutorials not listed here)

Mailing List

Please do subscribe to the mailing list, or use the archives to look for announcements:

  • To subscribe use this link for the Web interface or send an e-mail to "GSAS-II-request at" GSAS-II-request@…. Use subject subscribe (or subscribe <password> where <password> is your preference for a mailing list login password).

GSAS-II Project tracking

Updates to the source code can be followed using the Timeline Trac tool at this website. To enter a ticket, send an e-mail to Brian Toby. The Roadmap feature is not currently in use.

GSAS-II Developer Notes

Miscellaneous Notes for Code Developers

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