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
>>
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