II - Crystallography Data Analysis Software

This is the former Home Page for GSAS-II

Information at these pages is out-of-date. Please use web site https://gsasii.github.io/ for information on GSAS-II

GSAS-II is a unique and comprehensive open source Python project for determination of crystal structures and diffraction-based materials characterization for crystalline solids on all scales, from perovskites through proteins, using both powder and single-crystal diffraction and with both x-ray and neutron probes. Refinements can combine measurements from laboratory and synchrotron x-rays as well as constant wavelength or time-of-flight* neutron sources. It provides structure solution and refinement as well as extensive visualization capabilities.

Many capabilities of GSAS-II are unique to GSAS-II or are only found in software with very limited scope. For magnetic scattering, all possible color subgroups can be derived and explored. With powder diffraction, GSAS-II supports all stages of data reduction and analysis, including area detector calibration and integration, pattern indexing, LeBail and Pawley intensity extraction and peak fitting. Pair distribution functions (PDF) can be computed from high-energy x-ray diffraction. Instrumental profile parameters can be fit to data from standards or derived from fundamental parameters; sample profile effects (crystallite size and microstrain) are treated independently from the instrument. When large numbers of patterns are measured with parametric changes in measurement settings, GSAS-II provides a novel capability to fit all patterns in a single sequential refinement with subsequent parametric fitting. GSAS-II also provides small-angle scattering and reflectometry fitting and simulation of the effects of stacking faults.

Installation instructions

See this link for installation details

Please Cite

The primary citation for GSAS-II is:

Toby, B. H., & Von Dreele, R. B. (2013). "GSAS-II: the genesis of a modern open-source all purpose crystallography software package". Journal of Applied Crystallography, 46(2), 544-549. doi:10.1107/S0021889813003531

If you use GSAS-II in any part of your project, please cite it in your publications. This is the only way you can demonstrate your support of the project. (Citations to GSAS-II have ~doubled every year, with 104 citations in 2017.) Note that some sections of program utilize work by others and will display citations for that. If you use those sections, please cite those papers as well.

Tutorials

To learn how to use different parts of GSAS-II, we strongly encourage running the tutorials here.

For background material on powder diffraction crystallography, see the links on our Powder Diffraction Crystallography Educational Materials page.

GSAS-II Documentation

In the future we hope to increase the amount of documentation available but for now this is what is available:

Help: (https://advancedphotonsource.github.io/GSAS-II-tutorials/help/). This is not always complete, but this has been reworked and contains a lot of information (also available as a .pdf document. Please do let us know about things that need to be added here.

Tutorials:(https://advancedphotonsource.github.io/GSAS-II-tutorials/tutorials.html)]. This is the best place to start with GSAS-II.

Developer Notes: https://advancedphotonsource.github.io/GSAS-II-tutorials/documentation.html#developer-s-documentation >450 pages of code documentation generated from comments in the code and some documentation files are found on the "Read The Docs" web site. This provides documentation for code developers, for people interested in command-line access to GSAS-II or for the curious. We invite people interested in developing or extending GSAS-II. The code is open source and we are happy to review submitted code or consider collaborations.

Mailing List

Please do subscribe to the mailing list. Note that we often reply to questions directly to the sender to reduce the amount of traffic on the mailing list so the list will not generate a lot of "spam." You can also browse/search the archives here: http://www.mail-archive.com/gsas-ii@mailman.aps.anl.gov/.

To subscribe use this link for the Web interface or send an e-mail to "GSAS-II-request @ mailman.aps.anl.gov" (remove spaces). Use as the subject subscribe (or subscribe <password> where <password> is your preference for a mailing list login password).

Bugs

We frequently get bug reports without enough information to find what is wrong or that might have already been fixed. Before reporting a bug, please confirm you are using the newest GSAS-II version (see Help-->"Check for Updates"). If in the latest version, and we can reproduce your bug, we will work on fixing it. Suggestions for improvements are also welcome.

To report a bug, see this page.