File has been modified...

This message occurs when EXPGUI detects that the experiment file has been changed by another program. (EXPGUI only tracks the file modification date, so that the file could have been opened for writing, but no actual changes were made.) This can be normal behavior -- for example after a refinement cycle has been run, or this can signal a problem, such as two people or sessions trying to edit the same .EXP file. This warning is made because a choice must be made: to keep the version currently displayed in EXPGUI, or to use the new version written by the other program. On UNIX, this message can be avoided by setting the Autoupdate EXP flag to "on" causes .EXP files to be loaded automatically after GSAS programs are run, eliminating most occurances where this message is displayed, but with the disadvantage that a bad refinement run can not be reversed easily.

• If you choose to keep the currently displayed version and make changes and then save the file, either by using the File/Save menu option or by running a GSAS program, the new version just written will be lost. This can be useful to discard the results of a refinement that has gone awry but in other cases can be a setback.
• If you opt to load the new .EXP file, by pressing "Load new", the version currently displayed in the EXPGUI window will be lost. This is normally what you will want to do, but if you unsure, you can select "Continue with old", use File/Save As to save the version in EXPGUI and then use "EXPNAM" to load the new version, so they can be compared.

If unsaved changes have been made to the experiment file in EXPGUI, and the file us changed by an external program, the message "you have made changes to this version" is added and a third button, "Save edited version", is shown. Under this circumstance, the usual action, pressing "Load new" could result in desired changes being lost. Pressing "Save edited version" results brings you to the File/"Save as" menu, where the modified version of the experiment file in EXPGUI can be saved under a new name.

Input a value for the title

A dialog with "Enter a value for the title for experiment..." appears when a new experiment is created. Note that this title can be edited later on the Least Squares Control Page.

Unix File Conversions

In UNIX, GSAS data, experiment and instrument parameter files are expected to have a format with exactly 80 characters per line and no line separators (no carriage returns or linefeeds). Files in this format are called "Direct Access". Normal UNIX files may have any number of characters per line and every line is terminated by a line feed character. These files are called "sequential". EXPGUI uses the convention that all uppercase is used for Direct Access files while all lowercase is used for sequential files.

The Unix File Conversion menu is used to convert sequential files to direct access for use in GSAS or to convert direct access files to sequential, for use in standard UNIX programs, such as editors or e-mail.

Windows File Conversions

In Windows, GSAS data, experiment and instrument parameter files are expected to have a format with exactly 80 characters per line followed by a carriage returns and a linefeed (82 characters total per line). Files in this format can be read in "Direct Access" mode. The Convert menu in windows can be used to convert files into this format (it can also convert UNIX direct access files correctly). The original version of the file is retained and renamed.

Compute Composition

The composition box shows the unit cell and asymmetric unit composition for all phases in a material. Site multiplicities and occupancies are taken into account.

Export coordinates in MSI .xtl format

The Export/exp2xtl routine writes a .xtl file, as is used in Insight-II and Cerius2 (Molecular Simulations, Inc.). Note that spacegroups are not named exactly the same in the two programs and the origin may need to be specified as "origin 2", for spacegroups where the center of symmetry is not at the origin. It is up to the user to get things right.

Delete History Records

Every time a GSAS program (including EXPGUI) is run, an entry is added to the "history records" in the .EXP file. After 999 entries have been written, no more can be added to the file. Further, reading large numbers of history records can slow the GSAS programs (this is less of a problem on faster computers). For these reasons, it may be a good idea to prune the older history records from the file. If more than 100 history records are found in an experiment file, EXPGUI suggests that the older history entries be deleted. Alternately the File/EraseHistory command can be used to invoke the this option.

On the dialog the number of history records to be retained is specified. Also, after records have been deleted, the remaining records can be renumbered starting with 1, so that the 999 record limit is not reached.

Abandoning Constraint Editing

If the "Cancel Changes" button is pressed when a profile or atom contraint is being edited or created, a message saying "Do you want to lose any changes made to this constraint?" is displayed, even if no changes have been made to the constraint. Changes are recorded only when the "Save" button is pressed.

Choose CIF Block

When coordinates/cell parameters are read from a CIF, all blocks in the file are read. If more than block containing coordinates is found, a message saying "More than one block in CIF contains coordinates. Select the block to use." One must then select one of these blocks from the list of blocks. The blocks with coordinates are listed, both numbered and with the block (data_) name. The "CIF Browser" button can be pressed to view the data names and their values for each block.