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UNIX-Specific 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, both formerly 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).

GSAS runs on Windows computers and under two (three?) variants of UNIX: Linux (Intel), Irix (SGI) [and Macintosh OS X]. This page describes notes on use of GSAS with UNIX. Note, read read my platform-inclusive GSAS web page before reading this page.

Installing GSAS on UNIX Systems

0. GSAS System Requirements

Earlier versions of GSAS were available for VAX, HP-UX and Ulrix, but at present GSAS is distributed for the following operating systems:

Silicon Graphics:




Approximately 50-80 Mb of disk space is needed to load GSAS on any platform. About 10 Mb of this can be reclaimed after the installation is complete.

1. Methods for running GSAS

Two mechanisms are available for running GSAS, as described below. Note that the "Default GSAS definitions" (gsas.cshrc) and tkGSAS are no longer being supported.
1.1 The Standard GSAS script
This is a short c-shell script that is invoked by typing "gsas". It offers a number of commands that are used to invoke GSAS programs and operations. Many, but not all, UNIX commands can be run from inside the gsas script. This script is distributed as part of GSAS.
1.2 EXPGUI: A Graphical GSAS User Interface and Experiment Editor
This allows access to a subset of GSAS features in a convenient GUI environment. All features are still accessible using the original command-driven interface.

2. Downloading GSAS

The GSAS distribution kit for Linux and SGI consists of a tar file specific to the computer system being used. For Linux, SGI and OS X a single file with GSAS, EXPGUI and the Tcl/Tk package is also available See links for SGI & LINUX or for Mac OS X. The latter choice is usually easier.

3. Installing the GSAS script

To use the GSAS script, all that is necessary is to create an easy way alias the script. One way is to add an alias to each user's .cshrc file so that typing the command gsas will start the script:

                cat >> ~/.cshrc
                alias gsas /usr/local/gsas/gsas
Another way is to create a file which will execute the gsas script from a command in your system's path.
                cat > /usr/bin/gsas
                chmod +x /usr/bin/gsas
Note that in the above commands ^D means control-D.

4. Concluding Notes

At this point you are now ready to use GSAS. Everything that is described in the present GSAS manual the same except that unix style file paths must be used for the exercises rather than windows names. For example, use
for the data set name in the first exercise. (Your path may differ if GSAS was loaded in a location other than /usr/local/gsas).

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

GSAS is Copyright, 1984-2004, 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:
Last modified 09-February-2005 by website owner: NCNR (attn: Craig Brown)

$Revision: 1.4 $ $Date: 2004/10/05 18:42:39 $