Hi, Scott, In fact, I have a series of single crystal Ni-Fe alloys (Fm-3m) with known atomic ratio, and measured both Fe and Ni edges for samples and standards. I just want to see if there's any difference between the local bonding environment of Fe and Ni, such as R, N and sigma2. Now using the suggested method by Matt by changing atoms in FEFF.inp file, I can only get ss, deltr and E0 from fitting (I don't know how to refine N and R). But the fitting with Ni (or Fe) edge can only generate the same R and deltr for Ni-Ni and Ni-Fe pairs. Fitting the edges of Ni and Fe will yield a little difference in the R and deltr. Which results should I believe, or something wrong I am using the program because I cannot generate different R for Ni-Ni and Ni-Fe pairs with the same data set. Many thanks for your suggestions and helps.
Fuxiang Zhang On Thu, Jun 23, 2016 at 4:23 PM, Scott Calvin <dr.scott.cal...@gmail.com> wrote: > One additional thought: > > Distinguishing Ni-Ni and Ni-Fe by creating two different feff paths and > fitting the spectrum as a mixture of the two is very difficult, to put it > mildly, as both Anatoly and Matt indicated. > > But the bond length determined by your fit *may* be able to give you a > clue, particularly when compared to appropriate standards. Depending on the > details of your structure, the average bond length may depend on the > fraction of sites occupied by iron to a degree which is measurable by > EXAFS. Even if you simply use a nickel-nickel scattering path in feff to > model your structure, differences in bond length could be indicative of > changes in site occupancy. > > Ideally, this could be done by creating a series of standards with known > iron-nickel ratios, fitting the bond length for each, and then comparing a > fit of a sample with a similar structure but unknown iron-nickel ratio to > the results for the standards. > > —Scott Calvin > Sarah Lawrence College > > On Jun 23, 2016, at 3:41 PM, Fuxiang Zhang <zhan...@umich.edu> wrote: > > Hi, Matt and Anayoly, > Thank you very much for the help. > > Fuxiang > > On Thu, Jun 23, 2016 at 1:51 PM, Anatoly I Frenkel <afren...@yu.edu> > wrote: > >> Whatever you decide to do, remember that Ni Ni and Ni Fe pairs look very >> similar by EXAFS, so it does not matter how you end up doing it. >> You can as well use pure Ni but you may want to consider both fcc and bcc >> structure for making the model because the alloy may end up to be either >> that or that, especially if it is a nanoalloy. >> >> Anayoly >> >> >> >> Sent from my Verizon Wireless 4G LTE Tablet >> >> >> -------- Original message -------- >> From: Fuxiang Zhang <zhan...@umich.edu> >> Date: 6/23/2016 12:51 PM (GMT-05:00) >> To: ifeffit@millenia.cars.aps.anl.gov >> Subject: [Ifeffit] How to input atoms in solid solution for Artemis >> >> Hi, All, >> I am new in using EXAFS techniques. Just wondering how to input atomic >> structure of NiFe solid solution to Artemis. It has a simple Ni-structure, >> but both Ni and Fe occupy the same site. If I use partial occupancy, >> Artemis program does not allow. Anyone can give me an ideal? >> Also the coordination number N cannot be refined in this simple system >> (12), is that right? In fact I just want to get the N through the fitting >> of EXAFS because of the partial occupancy. >> Thank you very much >> >> Fuxiang Zhang >> >> _______________________________________________ >> Ifeffit mailing list >> Ifeffit@millenia.cars.aps.anl.gov >> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit >> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit >> >> > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit > > > > _______________________________________________ > Ifeffit mailing list > Ifeffit@millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit > >
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit