Hi Carlos,

Please clarify somethings for me regarding your inquiry.
You have a structural model and you have data.
You calculated a FEFF simulation of your structural model.
You did not use the FEFFNNNN.dat files to try to fit the model to your data,
but instead just did a comparison of the simulated chi(k), presumably
with just some default settings in FEFF.inp in addition to your structural model.
Is that correct?

Generally, it is the fit to the data that gives one feedback on the validity
of the structural model (GIGO rules apply).

If you have a model, then you have a model coordination number and can use
a program (e.g. Artemis) to refine amplitude, distance, mean-square-relative displacement
and energy shift. Do you need explanations of what these parameters represent?

So, to address what you were wondering, I believe the answer is yes...you need to actually
do a fit, and the goal isn't to get the obtained spectrum to look like your simulation.
Data is sacred. The goal is find a model that best reproduces the data (within a confidence
level governed by the goodness of fit).

regards,
Robert

On 11/5/2015 7:06 AM, Carlos Triana Estupinan wrote:

Dear 

Bruce

I am doing calculation of EXFAS for a amorphous structure created by molecular dynamics. I am using FEFE to obtain chi(k) and the file xmu, however, when comparing with experimental data with the calculated EXFAS I have the following problems.

1) The Fourier transform of the EXAFS calculated by FEFF has the same shape that the experiment spectra, however it is higher in amplitude. 

2) The calculated EXFAS by FEFF has the same oscillation in K-space, but it does not match the oscillation in K (both of them are shifted to each other).

I am wondering if I need to do an extra correction to the calculated EXAFS by FEFF in order to match the K-space and the amplitude in R-sapace. Shall I change the energy shift or the Edge step to match the experimental spectra. I so, how can I am sure about the obtained spectra really correspond to my molecular dynamics simulation.

Thanks for your help.

Regards.
​

2015-11-03 13:42 GMT+01:00 Bruce Ravel <bravel@bnl.gov>:

On 10/28/2015 08:44 PM, 百度知道用户 wrote:

Hi all,
I processed a series of data using IFEFFIT Athena, and saved it as a
project. Later, when I opened the project in IFEFFIT Athena, the plot
window did not show the curve. I tried to open the project in Demeter
Athena, but  popuped "Can't call method "datatype" on an undefined
value". The data curve was also not shown. I want to know what happened
to this? Are the data damaged? I am very thankful if this problem can be
solved.

It is hard to address a problem like this without an actionable bug report.  See http://bruceravel.github.io/demeter/pods/bugs.pod.html

B

--
 Bruce Ravel  ------------------------------------ bravel@bnl.gov

 National Institute of Standards and Technology
 Synchrotron Science Group at NSLS-II
 Building 535A
 Upton NY, 11973

 Homepage:    http://bruceravel.github.io/home/
 Software:    https://github.com/bruceravel
 Demeter:     http://bruceravel.github.io/demeter/
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--

Carlos Augusto Triana Estupiñan (C.A. Triana-E)
Physicist
M.Sc. In Physical Sciences-Research
PhD Student-Research
Ångströmlaboratoriet, Lägerhyddsv. 1
Solid State physics
Uppsala University, Box 534
751 21 Uppsala, Sweden
Tel: +46 018 471 3144
e-mail:carlos.triana@angstrom.uu.se
web:http://www.uu.se/

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