On Friday 20 July 2007, Yuan Ping wrote:
Hello Bruce,
Thank you for sharing your software. I found IFEFFIT in google and installed it recently in my MAC OSX computer. Trying to learn how to use it, I took a sample chi_k data (Al, k-edge) and played with the fitting in Artemis. One problem I can't solve by myself is that no matter how I chose the k range, r range, dr, dk, the fitting always stops at k~ 3 even though the data covers k= 1-8. So in the plot, the fit curve is much shorter than the data. Is this a plotting problem or a fitting problem? I've saved and attached the project to this email.
Thank you very much for your attention. Yuan
Hi Yuan, First off, I want to apologize for the tardy response. Your message to the mailing list arrived at a time when I was very busy. Fortunately, I noticed the email this afternoon while reading other email. The problem you are seeing is due to the unfortunate confluence of two things: (1) the chi(k) data that you imported into Artemis does not start at k=0, and (2) you are using a very old -- version 0.8.002 -- version of Artemis. Versions of Artemis from 0.8.007 on will recognize when the chi(k) data you import is not on Ifeffit's standard k grid and interpolate. So, if you were using a more up-to-date version of Artemis, you would not have seen this problem. You have two choices to fix this problem: 1. Update the Ifeffit package on your machine and rebuild your project file. http://cars9.uchicago.edu/iffwiki/Downloads 2. If you must, for some reason, continue using the old version of Artemis, you will have to do the interpolation yourself. Artemis expects the data to be on a k-grid that starts at 0 and goes in steps of 0.05 invAng until the end of the data. The most direct method of putting chi(k) data into Artemis is to read it directly from the Athena project file. That is, using the Open file dialog in Artemis, select the Athena project file and use the Athena project dialog in Artemis to select your chi(k) data. Regards, B -- Bruce Ravel ---------------------------------------------- bravel@anl.gov Molecular Environmental Science Group, Building 203, Room E-165 MRCAT, Sector 10, Advanced Photon Source, Building 433, Room B007 Argonne National Laboratory phone and voice mail: (1) 630 252 5033 Argonne IL 60439, USA fax: (1) 630 252 9793 My homepage: http://cars9.uchicago.edu/~ravel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/