Starting GSAS-II

A video version of this tutorial is available at

Starting GSAS-II is done in different ways, depending on your OS and how GSAS-II is installed.

One common way is start a console window, set the current directory to the location of GSAS-II  and then enter:




This will work if the default Python is as described in the GSAS-II Wiki pages you found when downloading GSAS-II, otherwise you may have to enter the correct path for that version of Python.


On Windows, the installer will usually create a RunGSASII.bat file in the main GSASII directory and place a shortcut to this file on the Desktop, but it can be moved where desired.


On the Mac, the installer creates a file in the main GSASII directory, which can be dragged to the doc. One can create a shortcut to this file and the shortcut can be moved, for example to the desktop, but do not move the file.


When GSAS-II starts, you should see three windows, two of which are almost empty. The topmost one is a vertically split window; we will refer to this as the Data Window. The left side will contain a tree-like outline of your GSAS-II project as you add data, phases, etc. The right side will contain a display of data depending on your tree item selection; you can change many of the items in this display depending on how you wish to use GSAS-II. The second window, immediately under the first is labeled GSASII Plots; this will contain tabbed graphical displays, when appropriate, corresponding to the selected tree item. This may be a crystal structure, powder pattern plot, etc. The tabs allow you to view any recently produced plot. You may be able to interact with the current plot via the mouse thus changing items in the data window; for example picking powder pattern peaks from the powder pattern will add entries to the displayed peak list.  The third window is the GSAS-II console; it will display error messages, some results of calculations (e.g. residuals from a refinement), etc. No input is taken from the GSAS-II console as all interaction is via the GUI. These windows may be moved anywhere on the screen or to a different display (real or virtual); GSAS-II will save the locations of the first two when GSAS-II is exited. On a new start, they will reappear in the saved locations (or else centered on the main computer screen if they are now off screen). On Linux and Windows a menu bar appears at the top of the Data Window; on a Mac this menu will appear in the system menu bar location (usually at the screen top). The items in the menu bar are separated by a vertical bar; those to the left “File …” are global for the GSAS-II project and those to the right (if any) are for the specific data displayed on the right side of the Data Window. On my Windows machine the screen looked like:


 The project file contains all data and results related to the project you are working on. (Exception: image files are not stored in the project; to save space only the file name is saved.) The console window displays a banner and some information about the version of Python and the packages used by GSAS-II. This console window will display important information as data processing by GSAS-II proceeds. You may wish to cut-and-paste parts of this window to another place if desired.



For Windows, we suggest that you change the properties of this window to (in Windows: Properties/Layout) to have 9999 for the height and 150 for the width and to allow “QuickEdit Mode” (if available) for easy cut/paste operation. You can perhaps also change the font, font size, font color and background color if desired. These settings will be retained for subsequent uses of GSAS-II.