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Information about GSAS

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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?

Where can I get an up-to-date GSAS 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).

GUI tools for GSAS



Bugs in GSAS or EXPGUI

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, 1984-2001, 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:
Last modified 09-February-2005 $Revision: 1.12 $ $Date: 2005/02/09 21:11:52 $