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Satellite Workshop 11—Introduction to the GSAS-II Crystallographic Analysis System

May 9, 2013 (all day)
Bldg. 401, A1100

Organizers: Robert B. Von Dreele and Brian H. Toby (APS)

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OVERVIEW

The workshop will introduce the attendees to the use of the new GSAS-II software package for the reduction, solution and refinement of crystallographic data, with particular emphasis on powder diffraction data. All software needed to install and run the software is freely available. Attendees will be required to bring their own laptops with the software already downloaded. The workshop will be targeted toward individuals with some experience with Rietveld analysis and to experienced single-crystal crystallographers with some knowledge of powder diffraction.

Background: The GSAS-II software suite will be the eventual replacement for GSAS and its associated graphical user interface (GUI) package, EXPGUI, which are likely the most widely used crystallography software package for materials crystallography, particularly for neutron and synchrotron powder diffraction (Rietveld) fitting, but GSAS also see use for neutron single-crystal analysis and combined x-ray single crystal/neutron powder diffraction analysis. As one measure of their importance, GSAS and EXPGUI together have received >7,000 citations and continue to be cited many hundreds of times annually.

The GSAS-II package has much wider goals than GSAS. Although over time its capabilities will continue to advance, the GSAS-II package already has capabilities needed for all aspects of powder diffraction crystallographic analysis, including area detector data reduction, indexing, and structure solution by charge flipping, in addition to the refinement and Fourier map analysis capabilities that duplicate GSAS features. GSAS-II can be used for analysis of constant-wavelength x-ray and neutron powder data, as well as x-ray and neutron single-crystal data. Oak Ridge National Laboratory has indicated an interest in driving the adaptation for time-of-flight neutrons. GSAS-II is a completely modern code, written almost completely in Python and designed with a sophisticated GUI and with advanced visualization features integrated. GSAS-II is open source and is freely distributed. GSAS-II has recently been made available to the public, with the understanding that new capabilities are being added and bugs addreseed on a continuing basis.

Because GSAS-II includes an area detector calibration and integration module, the software may be of interest within the APS where powder diffraction is used for calibration of area detector placement, or where radial integration is used.

Program: The target audience for this workshop will be individuals who have at least some experience with Rietveld analysis and experienced single-crystal crystallographers who have not performed powder diffraction experiments, but have at least some familiarity with the technique. However, attendees wishing to use GSAS-II only for beamline data processing will have no difficultly following the first section of the course . Attendees should bring their own laptops (Windows, Mac and Linux are all supported) and should install GSAS-II prior to the workshop. Help will be provided at the workshop to help install the software for anyone who has had trouble.

The format of the course will be to alternate between short overview lectures, demonstrations of the program and hands-on exercises.  Examples of some of the exercises can be seen from the tutorial present on the GSAS-II web site, https://subversion.xray.aps.anl.gov/trac/pyGSAS.

APPROXIMATE WORKSHOP TIMELINE

8:00 Coffee, tea and software installation support
9:00 An overview of GSAS-II capabilities
9:45 Area detector data reduction demo
10:00 Coffee break
10:20 Self-paced exercise 1: Area detector data calibration and reduction
11:00 Autoindexing, charge-flipping and Fourier demo
11:20 Self-paced exercise 2: Autoindexing, structure solution & completion
12:00 Lunch break
1:30 Self-paced exercise 2, continued
2:15 Introduction to GSAS-II refinement capabilities and Rietveld demo
2:45 Self-paced exercise 3: Rietveld refinement exercise
3:30 Coffee break
3:50 Overview of restraints and constraints
4:10 Planned future developments for GSAS-II
4:30 Participant feedback on potential improvements, development priorities and other perceived needs
4:50 Adjourn

Updated 12/09/13