On Wednesday 05 May 2010 07:56:47 am baran yildirim wrote:
My problem is similar; I am trying to simulate a doped crystal (different than chp 10 in Atemis doc, this time impurity atom is subjected to XAS) and the host is similar to inverse-spinel type: include both tetrahedral and octahedral sites in its structure. The dopant may settle in tetrahedral or octahedral sites.
Indeed. Similar enough that you also should read the paper by Scott Calvin that I suggested to Maria Elena.
1- I managed to simulate the doped structure as changing the FEFF inp file manually (first I run Atoms as if impurity ions settle in all sites and then keep it in 0 potential and change the 1st potential with the original atom) and did it for both sites, thus i have 2 batch of paths and then fit it. It seems it works (Question: Do you think what i am doing is logical? or any other suggestion? )
I think that's a good approach. Question 15 at http://cars9.uchicago.edu/ifeffit/FAQ/FeffitModeling gives a bit more information. The link to the page authored by Scott is quite useful.
2- But problems do not end :) Another problem is impurity ion may take different valences: it can be trivalent or divalent. In FEFF 9.0 i found kinda solution using ION command, it doesnt do what i exactly want but i can get some idea on what happens if the charge distribution changes. But unfortunately, i cant try it in ARTEMIS since i can not install FEFF 9.0 in ARTEMIS. As far as i understood the program structure is changed completely. But I didnt give up :)I generated the chi file in FEFF 9.0 and load it in ARTEMIS and continue to analyze but the results are not promising. (Question: Is there any way to run it together? and any suggestion in changing the valance? )
Artemis does not support Feff9 at this time. I actually have not played around with Feff9 yet, myself, so I won't be able to help with the rest. Perhaps one of the Seattlites can help .... B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/