[Ifeffit] E0 for bulk crystals and nanoparticles

[Frenkel, Anatoly]

That's true - if there are no "shift-like" changes in XANES, E0 may be constrained.
 
Anatoly

________________________________

From: ifeffit-bounces at millenia.cars.aps.anl.gov on behalf of Scott Calvin
Sent: Sun 2/25/2007 10:20 PM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] E0 for bulk crystals and nanoparticles



Hi again,

Hmm...Anatoly makes good points here. But I'd say that most of those
kinds of things should give changes in XANES. If you don't see
changes in XANES as you change the temperature, I'd still feel pretty
comfortable constraining the E0 to be the same for all temperatures
between 10 and 300 K. And that lets you decouple E0 from lattice
expansion and the third cumulant, which was your goal.

--Scott Calvin
Sarah Lawrence College

At 10:06 PM 2/25/2007, Anatoly wrote:
>Leandro - depending on the details of your system and treatment,
>electronic structure of the nanoparticle may or may not change at
>elevated temperatures. It may change as a result of hydrogen
>chemisorption, charge exchange with support, ligand desorption,
>oxidation, etc. As a result, you may observe changes in XANES that
>may be due to the change in core hole screening or Fermi energy
>change or both (depending on the degree of "metallicity" of the nanoparticle).
>
>There are many references in literature demonsrating each effect
>that I mentioned.
>
>Thus, keeping E0 the same at all temperatures may or may not be
>wise, depending on the magnitude of the edge shift that can, in
>principle, be observed at different temperatures. If that happens,
>you may want to compare the resuls obtained by keeping E0 the same
>vs those when E0 was allowed to vary independently for each scan.
>
>In short, there is no "one fits all" answer.
>


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