First of all, kudos to Bruce and Matt on the new versions. One of my summer students more than once uttered the phrase "This is <italic>awesome</italic>" as she tried out yet another new feature. I concur. :)
Awwwww..... now I'm blushing.....
In my opinion, the path finder limit in feff is high enough for most applications. I frequently fit up to 5 angstroms, which, considering the difference between reff and r and the width of EXAFS peaks, means I feel I have to include paths up to about 6 angstroms. But that means I need to have feff compute a cluster bigger than that (as has been discussed on this list a few times)...which makes a 7 angstrom cluster seem reasonable; maybe 8 for safety. I have never encountered a path with more than 4 legs that I found to be significant.
2) Does anyone out there run into cases where paths with more than 4 legs are significant? If not, Artemis should just stick the card NLEG 4 into the feff.inp file automatically...that's probably a better default value. Of course, a knowledgeable user could still override that to include more legs if they wished.
The NLEGS suggestion is a good one. I'll probably take you up on it. The fix is very simple and is one that anyone can implement immediately without modification to the artemis source code. Search among the files installed as part of my software for a file called "feff.atp". This is template that Artemis uses to write input data for feff. In short, it provides a sort of outline for what the feff.inp file should look like. Simply add a line that says NLEG 4 somewhere in that file. On a unix machine, you will probably need to copy the feff.atp file to ~/.horae/atp/ before editing it.
1) Artemis now does a decent job of flagging users when iffeffit encounters a problem. Perhaps it should do the same for feff. (I know the feff error messages are often somewhat obscure. But if Artemis simply stated that "FEFF has encountered a possible problem" and advised users to check the messages screen, the behavior might seem a tad less baffling.)
Actually, I have been building a database of feff6 error messages. When Feff is finished, artemis parses the text in the window where the feff output is displayed. If it recognizes the error message, it displays an explanation in gaudy red-on-white text at the end of feff's run time messages. If you find a feff error for which Artemis does not provide an explanation, send me a project file that triggers the error so I can add it to the database for the next release. I am only making responses to the error messages from feff6L, the version that comes with Ifeffit, at this time. If you use another version of feff, you are on your own for now as far as recognizing what feff's error means. I have also been auditing the code this week to make sure that the messages window rises to the top of the screen when an informational message of this sort gets displayed. B -- Bruce Ravel ----------------------------------- bravel@anl.gov -or- ravel@phys.washington.edu *** My cell phone number has changed. Please ask if you need the new number Environmental Research Division, Building 203, Room E-165 Argonne National Laboratory phone and voice mail: (1) 630 252 5033 Argonne IL 60439, USA fax: (1) 630 252 9793 My homepage: http://feff.phys.washington.edu/~ravel EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/