Information about GSAS
GSAS (General Structure Analysis System) is a comprehensive system for the refinement of structural models to both x-ray and neutron diffraction data. The GSAS package can be used with both single-crystal and powder diffraction data (Rietveld analysis), even both simultaneously. Neutron data can be either from single-wavelength instruments, or for those a bit more masochistic, time-of-flight instrumentation. Up to 99 different sets of data can be modeled using mixtures of up to 9 different phases.
GSAS has been created by Allen C. Larson and Robert B. Von Dreele of Los Alamos National Laboratory. Executable versions of GSAS are distributed more-or-less freely (see the friendly message from the Regents of the University of California, below), but the source code is not distributed (don't complain to me on this one, I agree with you).
Where do I get GSAS?
I recommend installing GSAS & EXPGUI together. See this downloads page for instructions and links.
Note that there may be more recent versions of GSAS on the primary GSAS distribution sites:
- http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/gsas/public/gsas/ or
Note that you can install the combined GSAS/EXPGUI package and then upgrade to a newer version of GSAS, by overwriting the GSAS files with the "gsaskit" files. See the Windows or Unix installation information for more details.
Where can I get an up-to-date GSAS manual?
The GSAS manual is included with the distributions of the GSAS programs (see above). It is a ~230 page PDF file (1.7Mb) that contains three sections: tutorials, mathematical basis & file structures. Every GSAS user should take the time to read the "mathematical basis" section (pages 125-179 in 1/19/01 version)! The manual can also be found on-line: http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/gsas/public/gsas/manual/GSASManual.pdf The manual is what you should cite when publishing a structure refined with GSAS [and of course you will cite it: A.C. Larson and R.B. Von Dreele, "General Structure Analysis System (GSAS)", Los Alamos National Laboratory Report LAUR 86-748 (2000).]
Mirror sites for the manual:
What computers does GSAS run on?
GSAS runs in the various flavors of Windows, on Silicon Graphics computers running the Irix operating systems and in Intel x86-based Linux computers. An older version of GSAS runs in DOS using a 32-bit extension and an even older version of GSAS runs in openVMS (see below).
I have created a self-installing program that installs GSAS, EXPGUI and all needed support files: Installation notes.
It is also worth looking at the installation notes on the GSAS site: http://www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/gsas/public/gsas/windows/readme.txt even though the self-installer does all the hard work. There are also instructions on loading EXPGUI, if GSAS has been loaded from the CCP14 GSASKIT.EXE distribution in file expgui_Win_readme.html, but this may be out of date.
- Macintosh (OS X):
GSAS & EXPGUI now run on the Mac under 10.2 and later. The whole kit can be downloaded and installed via a single compressed disk image. See the OSX installation notes.
- Linux: Good news: there is a very easy way to load GSAS and EXPGUI onto fairly recent Linux systems that contain the RPM utility. See my rpm notes. If you cannot use the RPM, see the SGI information, below.
- SGI: My most recent instructions describe how to install GSAS and EXPGUI: expgui_Unix_readme.html. I also have some older notes on using GSAS with UNIX notes on using GSAS with UNIX.
- VMS: Despite the fact that GSAS was originally developed to run specifically (and exclusively) on VAX/VMS computers, the official VAX/VMS and AXP/VMS versions have not been updated in quite some time and never will be again. The most recent versions for VAX and AXP can be found at ftp://ftp.ncnr.nist.gov/pub/cryst/vms/gsas/. No support.
GUI tools for GSAS
EXPGUI is a a package that allows many of the most commmonly used features within GSAS to be accessed (but far from all of them). See the EXPGUI introduction or the EXPGUI full documentation.
The folks that have written GSAS get very little credit for their massive efforts. By including a reference to GSAS in your papers, you can help see that the citation index will reflect the importance of their contribution.
Much of the same is true for EXPGUI.
- A.C. Larson and R.B. Von Dreele, "General Structure Analysis System (GSAS)", Los Alamos National Laboratory Report LAUR 86-748 (2000). [link to PDF copy of manual]
- B. H. Toby, EXPGUI, a graphical user interface for GSAS, J. Appl. Cryst. 34, 210-213 (2001). [link to PDF version of paper]
FAQ for GSAS & EXPGUI
The CCP14 mantains a good set of links with tutorial and answers to a large number of GSAS-related questions: http://www.ccp14.ac.uk/solution/gsas/. The GSAS manual has a lot of answers, too. Anyone using the program should take the time to read the manual.
If you have installed EXPGUI on your computer, you have the complete set of documentation for that software. You can also find the same documentation at http://www.ncnr.nist.gov/xtal/software/expgui/expgui.html.
If you are new to GSAS & EXPGUI, I strongly encourage you to spend an hour or two running through a tutorial. I recommend starting with this: http://www.ncnr.nist.gov/xtal/software/expgui/tutorial3 as the data and web pages were intended to be "user-friendly."
There are also three tutorials in the GSAS manual. Two of these tutorials from the GSAS manual are repeated as as examples for EXPGUI: http://www.ncnr.nist.gov/xtal/software/expgui/tutorial1 and http://www.ncnr.nist.gov/xtal/software/expgui/tutorial2. These tutorials are intended to be read in parallel with the GSAS manual. There are also a number of tutorial examples on the CCP14 site.
In a moment of weakness, I started a web page to cover problems reported to me related to GSAS & EXPGUI: NCNR GSAS FAQ page. Send your contributions (preferably in HTML) for for inclusion on this page to crystal@NIST.gov
Bugs in GSAS or EXPGUI
Please convince yourself that the problem is not yours. (User errors are far more frequent than software bugs, IMHO.)
GSAS is written by: Allen C. Larson and Robert B. Von Dreele MS-H805, Los Alamos National Laboratory, Los Alamos, NM 87545. Problems, questions or kudos concerning GSAS should be sent to Robert B. Von Dreele at firstname.lastname@example.org
GSAS is Copyright, 1984-2001, The Regents of the University of California. The GSAS software was produced under a U.S. Government contract (W-7405-ENG-36) by the Los Alamos National Laboratory, which is operated by the University of California for the U.S. Department of Energy. The U.S. Government is licensed to use, reproduce, and distribute this software. Permission is granted to the public to copy and use this software without charge, provided that this notice and any statement of authorship are reproduced on all copies. Neither the Government nor the University makes any warranty, express or implied, or assumes any liability or responsibility for the use of this software.
Neither the author nor the U.S. Government makes any warranty, expressed or implied, or assumes any liability or responsibility for the use of this information or the software described here. Brand names cited here are used for identification purposes and do not consitute an endorsement by NIST.
Comments, corrections or questions: crystal@NIST.gov
Last modified 09-February-2005 $Revision: 1.12 $ $Date: 2005/02/09 21:11:52 $