Dear Shay,
Dear Rietvelders,
I agree with all who attributed this step to the metal filter (Ni for Cu
radiation) absorption edge jump.
In our lab, we got rid of this feature recently, when we migrated from
an older Bruker D8 Advance Series II with LynxEye detector
(Bragg-Brentano setup with Ni filter) to a D8 Advance A25 with LynxEye
XE-T. Operating the XE-T in high energy resolution mode discriminates K
beta electronically, making the Ni filter obsolete and thus removing the
edge jump.
However, I have to disagree with Matthew about TOPAS modeling this edge
jump "quite well".
(Disclaimer: I'm not running the latest version of TOPAS, and I'm
probably not up to date with the custom macros that are available in the
community. Thus, my statement might be outdated!)
I am using DIFFRAC.SUITE TOPAS version 5.
Firstly, this version of the macro contains a bug, which is described in
the supporting information of Lipp et al.
(https://doi.org/10.1021/acs.chemmater.2c00101). In a nutshell, the
parameter "cedge_scale", which is not declared anywhere, should actually
read "cedge_extra".
Secondly, it seems that the macro does not convolute the edge jump
feature with the sample related peak broadening. Empirically, the
absorption edge, like any other emission spectrum feature, is only
clearly visible if the peak is sharp enough. If you happen to have a
pattern which is composed of both very sharp and very broad peaks, and
optimize the edge jump macro parameters to model the jump left of the
sharp peaks, then also the broad peaks will have a sharp jump on top,
which should not be. I noticed this inconsistency because I usually
model the broad bump which is often caused by amorphous or
nano-crystalline material with a broad peak in a Peaks Phase. The
crystalline phase had sharp peaks with adsorption edge features, so I
tried to model this using the macro. While the bases of the sharp peaks
were now modeled nicely, the broad amorphous bump had an annoying sharp
edge jump on top.
To conclude, TOPAS with its versatile macro language certainly has the
potential to model this feature correctly, but the version of the macro
that I am aware of needs to be improved...
With best wishes,
Frank
--
Frank Girgsdies
Fritz-Haber-Institut der Max-Planck Gesellschaft
Department of Inorganic Chemistry / CatLab
On 04.09.2023 00:50, Matthew Rowles wrote:
Topas can model them quite well. The functionality was introduced in
version 5.
On Mon, 4 Sep 2023, 00:54 Kurt Leinenweber, <ku...@asu.edu
<mailto:ku...@asu.edu>> wrote:
Hi, Are these things modeled in Rietveld programs, by chance? It
seems like a lot of baggage to put in a refinement but if it makes
the results better…____
__ __
* Kurt____
__ __
*From:* rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>
<rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>> *On
Behalf Of *Thomas Gegan
*Sent:* Sunday, September 3, 2023 9:16 AM
*To:* Bish, David L <b...@indiana.edu <mailto:b...@indiana.edu>>;
Shay Tirosh <stiro...@gmail.com <mailto:stiro...@gmail.com>>;
Fernando Igoa <fer.igoa.1...@gmail.com <mailto:fer.igoa.1...@gmail.com>>
*Cc:* Rietveld List (rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>)
<rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>>
*Subject:* RE: [EXT] Re: [External] Re: Step-like basline____
__ __
I agree with a Ni absorption edge, possibly with a Kβ peak around
38° 2θ.____
__ __
*Tom Gegan*
Chemist III____
__ __
Phone: +1 732 205-5111, Email: tom.ge...@basf.com
<mailto:tom.ge...@basf.com>
Postal Address: BASF Corporation, , 25 Middlesex Essex Turnpike,
08830 Iselin, United States____
____
__ __
*From:* rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>
<rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>> *On
Behalf Of *Bish, David L
*Sent:* Sunday, September 3, 2023 7:08 AM
*To:* Shay Tirosh <stiro...@gmail.com <mailto:stiro...@gmail.com>>;
Fernando Igoa <fer.igoa.1...@gmail.com <mailto:fer.igoa.1...@gmail.com>>
*Cc:* Rietveld List (rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>)
<rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>>
*Subject:* [EXT] Re: [External] Re: Step-like basline____
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Hello Shay,____
I think it is probably related to "tube tails". You can read about
this in the literature (e.g., on the BGMN web site) and you can
model it in some Rietveld software such as Topas. You don't normally
notice this but it becomes apparent with higher-intensity peaks.____
__ __
Regards,____
Dave____
------------------------------------------------------------------------
*From:*rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>
<rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>> on
behalf of Fernando Igoa <fer.igoa.1...@gmail.com
<mailto:fer.igoa.1...@gmail.com>>
*Sent:* Sunday, September 3, 2023 3:06 AM
*To:* Shay Tirosh <stiro...@gmail.com <mailto:stiro...@gmail.com>>
*Cc:* Rietveld List (rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>)
<rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>>
*Subject:* [External] Re: Step-like basline ____
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This message was sent from a non-IU address. Please exercise caution
when clicking links or opening attachments from external sources.____
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Hey Shay, ____
__ __
Are you using a motorized slit during the measurement? These may
open up abruptly to compensate for the angular dependence of the
footprint and thus generate an abrupt increase in the intensity. ____
__ __
Hope it helps :)____
__ __
On Sun, Sep 3, 2023, 8:50 AM Shay Tirosh <stiro...@gmail.com
<mailto:stiro...@gmail.com>> wrote:____
Dear Rietvelders ____
I am attaching a zoom-in on a diffraction profile. ____
My question is what is the origin of the step-like profile next
to a very large reflection peak?____
Is it a sample preparation problem?____
Is it part of the baseline? ____
____
Thanks____
Shay____
-- ____
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____
____
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____
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