[Ifeffit] Phase shift

Matt Newville newville at cars.uchicago.edu
Tue Apr 10 22:04:22 CDT 2018


Hi Julian,



On Tue, Apr 10, 2018 at 1:30 PM, Julian Ehwald <jehwald at gmail.com> wrote:

> Dear all,
>
>
>
> I have a very general question about the phase shift. I tried to fit a
> rather noisy sample of Li2IrO3, where I get a first main peak around 1
> angstroem, according to FEFF calculation there should be something at 1.9
> and not any closer. This phase shift seems a bit too big to be true, is
> there something like an upper bound for a reasonable phase shift?
>
>
>
> Best, Julian
>

It's a little hard for me to tell what you mean.  Are you saying that Feff
predicts the peak of |chi(R)| to be at 1.9 Ang, or that the first shell
distance should be 1.9 Ang?

Phase-shifts for single-scattering peaks typically cause the peak of
|chi(R)| to be ~0.5 Ang below the near-neighbor distance. That can vary
some, but I would be surprised for it to be as big as 1 Ang.

It might be useful to post the data.

--Matt
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