[Ifeffit] Modelling texture in Artemis

Kirstine Dalgaard kjd at inano.au.dk
Mon Aug 20 05:35:51 CDT 2018

Dear Matt

Thank you for the advice. I could figure it out myself, if I know how the POLARIZATION parameter is interpreted or defined.

Where can I find that information? I found this on my own:

"This card specifies the direction of the electric field of the incident beam, or the main axis of the ellipse in the case of elliptical polarization. x, y, z are the coordinates of the nonzero polarization vector?"

But I lack a definition of the coordinate system - the polarization direction with respect to what, exactly?



From: Kirstine Dalgaard
Sent: Thursday, August 16, 2018 5:27 PM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: Re: Modelling texture in Artemis

(I am not sure this is the correct way to reply to this thread, hopefully it works)

Dear Matt

Thank you for your reply! The standard, which is highly textured, is NbSe2. The Nb K-edge was scanned.

The structure consists of layers with Nb coordinated to 6 selenium atoms in a trigonal prismatic manner. Thus, the environment is not isotropic. The nearest Nb-neighbors are e.g. only in the plane of the layer.

The preferred orientation is with the stacking-axis perpendicular to the pellet plane.

I then assume that I do have an effect of the non-random orientation of bonds/paths relative to the X-ray polarization?

On slide 28 in this presentation by Bruce Ravel http://xafs.org/Workshops/NSLS2002?action=AttachFile&do=get&target=Ravel.pdf it is stated that:

"FEFF is capable of computing the effect of polarization directly. The polarized theory is easily used in analysis with polarized data".

However, how do I implement this in my analysis? Is there maybe a written guide?

Best regards


From: Kirstine Dalgaard
Sent: Tuesday, August 14, 2018 11:05 AM
To: ifeffit at millenia.cars.aps.anl.gov
Subject: Modelling texture in Artemis

Dear all

How can texture in a powder sample be modeled in ARTEMIS?

My samples are fine powders of a layered material, mixed with cellulose and pressed to pellets. The data were collected in fluorescence mode with a 45 degree tilt.

PXRD data reveal that the samples are highly textured, including standards.

I am new to XAFS, and I need some advise to deal with this issue.

Best regards

Kirstine Dalgaard
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