[Ifeffit] correlated Einstein model and Debye model
Renato Canha Ambrosio
rcanha at ccet.ufrn.br
Wed Feb 1 13:14:53 CST 2006
Good afternoon everybody
I have questions about the Einstein and Debye correlated models in IFEFFIT.
As described in page 80 of the EXAFS ANALYSIS WITH FEFF AND FEFFIT - PART 2:
COMMENTARY by Bruce Ravel the eins function is a function evaluated in the
context of the current path. So the reduced mass is calculated with the mass
of the atoms in the path. Its ok but I have several scans at different
temperatures so I would like to refine not only the Theta (Einstein
temperature) but also the reduced mass and perhaps the static disorder. Can
I do it in the context of the path or I have to perform a non - xafs
refinement with the file containing the temperatures and sigma^2. I make the
same question for the Debye correlated model.
Thank you very much for your kind attention
Renato Canha
Universidade Federal do Rio Grande do Norte
Natal - RN - BRASIL
Open WebMail Project (http://openwebmail.org)
---------- Original Message -----------
From: ifeffit-request at millenia.cars.aps.anl.gov
To: ifeffit at millenia.cars.aps.anl.gov
Sent: Wed, 1 Feb 2006 12:00:12 -0600
Subject: Ifeffit Digest, Vol 36, Issue 1
> Send Ifeffit mailing list submissions to
> ifeffit at millenia.cars.aps.anl.gov
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> or, via email, send a message with subject or body 'help' to
> ifeffit-request at millenia.cars.aps.anl.gov
>
> You can reach the person managing the list at
> ifeffit-owner at millenia.cars.aps.anl.gov
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Ifeffit digest..."
>
> Today's Topics:
>
> 1. Re: FEFF8 vrs FEFF6 (Matt Newville)
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 1 Feb 2006 08:54:22 -0600
> From: Matt Newville <newville at cars.uchicago.edu>
> Subject: Re: [Ifeffit] FEFF8 vrs FEFF6
> To: XAFS Analysis using Ifeffit <ifeffit at millenia.cars.aps.anl.gov>
> Message-ID:
> <b8522e3d0602010654j195cf712hf30b878a67bac08e at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> HI Shelly,
>
> I wouldn't say it's wrong to use Feff8 for EXAFS analysis, just
> rarely necessary.
>
> Feff8 was definitely designed for XANES, and improvements for EXAFS
> were not the main goal. But there are a few cases where Feff8 _is_
> known to be better for EXAFS than Feff6. (I'll leave out Feff7 as it
> seems no one is using this much). Clusters with H is one, and
> transuranic elements is another. I've heard a few people claim that
> Feff8 gives "better E0's", which I think means that E0 refines to a
> value closer to 0 (that is, to where the it's arbitrarily assigned in
> the data processing). Since E0 has to be refined and has little
> physical significance, I don't find this to be a compelling advantage
> for Feff8.
>
> Early versions of Feff8 (pre-release? Including 8.00?? I'm not sure)
> were much worse for EXAFS.This did get fixed, but I'm not sure when
> (I have a hard time understanding Feff8 version numbers and can never
> really tell which get released and widely used: I've given up
> complaining and live wih the fact that "Feff8" means one snapshot of
> 8 years worth of work.). By Feff8.1 for sure, and maybe eralier, there
> were essentially no difference between Feff6, 7, and 8 for EXAFS.
> That was based on analysis of data on metal foils (Cu, Ag, Au), and
> could hardly be called thorough and possibly not even 'highly
> relevent to real-world problems', as it doesn't even test changes in
> exchange or overlap of metal-oxygen potentials. Better testing and
> comparisons would be very good.
>
> Anyway, I think it's fine to use Feff6, 7, or 8 for EXAFS.
>
> I don't think anything should change for these versions in the
> reporting of how a Feff calculation was done for EXAFS. Most EXAFS
> work using Feff give no details about the calculation, and I think
> that's mostly OK, as the Feff/Atoms/Artemis default parameters are
> generally quite reasonable. If the work discusses comparing
> different Feff calculations, then obviously more detail on what was
> changing would be needed.
>
> That's my opinion, anyway.
>
> --Matt
>
> ------------------------------
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
> End of Ifeffit Digest, Vol 36, Issue 1
> **************************************
------- End of Original Message -------
More information about the Ifeffit
mailing list