[Ifeffit] iron carbide fitting with Artemis

[Yunyun Zhou]

Hello Mike,

Thank you very much for your help. I have a question about combining
different atoms in a shell. For example, in the Fe5C2 model,
 ATOMS                  * this list contains 221 atoms
 *   x          y          z     ipot tag           distance
    0.00000    0.00000    0.00000  0  Fe1           0.00000
   -0.19385    1.76888   -0.78107  4  C1.1          1.94335
   -0.19385   -0.94552    1.72493  4  C1.2          1.97661

If I am going to combine C1.1 and C1.2, shall I set them the cartisian
coordinate as in FEFF file?

 ATOMS                  * this list contains 221 atoms
 *   x          y          z     ipot tag           distance
    0.00000    0.00000    0.00000  0  Fe1           0.00000
   0.00000     0.00000    1.94335  4  C1.1            1.94335

Thanks a lot for your help again!

Best,

Yunyun


On Thu, Oct 26, 2017 at 4:40 PM, Mike Massey <mmassey at gmail.com> wrote:

> I definitely recommend combining multiple atoms of similar distances into
> the same path. That's what you end up with anyway if you use multiple
> paths, with a lot more potential problems in the software.
>
> Sometimes it is beneficial to split a shell of of atoms into two, to
> capture some physical behavior (for example, 2 atoms at 3 Angstroms and 4
> atoms at 3.3 Angstroms, instead of one very disordered shell of 6 atoms at
> 3.2 Angstroms).
>
> Depending on your data quality, I recommend building a fitting model with
> maybe 2-8 total "shells" of atoms at different distances.
>
>
>
> Mike
>
>
> > On Oct 26, 2017, at 12:52 PM, Yunyun Zhou <yyzhouzhou at gmail.com> wrote:
> >
> > Hello All,
> >
> > I am having trouble fitting my sample with both Fe5C2 and Fe3O4 as
> standards. Hopefully somebody could help me out and I really appreciate it.
> >
> > My iron sample was mainly iron carbide in the core and iron oxide on the
> shell. Fe5C2 has a monoclinic structure and generated complicated FEFF
> paths. Many of the paths have similar distances. I have found some paper
> reported their results as follows, which apparently combined several paths
> together and assume they have similar path length. My first question is
> does someone know how they did it? It seems that combing similar paths
> makes fitting much easier, but I am not sure whether this is a correct way
> to do the fitting.
> >
> > My second question is regarding fitting with the two combined models of
> Fe5C2 and Fe3O4. I haven't fit with two models before. Is it just like what
> I did in the attached Artemis file? Shall there be any restrictions between
> the two models and do I have to fix some of the parameters?
> >
> > Thank you very much in advance for your help!
> >
> > Best,
> >
> > Yunyun Zhou
> >
> > Fe5C2 FEff paths:
> > <image.png>
> >
> > Literature reported results:
> > <image.png>
> > <artemis_CWV 130 spent_example.fpj>
> > _______________________________________________
> > Ifeffit mailing list
> > Ifeffit at 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 at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20171026/de2c3ced/attachment.html>