[GSAS-II] GSAS-II Digest, Vol 303, Issue 1

Mon Apr 26 08:59:30 CDT 2021

Hi,
I would like to add, after Jeremy's e-mail, that I like to use a standard
material that is similar to the samples I study frequently since sample
transparency in reflection mode will have an influence on peak widths and
sometimes the best particle size and microstrain free sample will still
give broad peaks if the absorption of X-rays is low and penetration depth
is important. In such cases even inhomogeneities in packing density will
play a role in your peak shape.

I usually work with perovskites or metal-organic compounds containing
lanthanides and 3d metals, so Y2O3 is a good compromise regarding
absorption. Additionally, Y2O3 powder is stable for many years, not prone
to absorption of water or CO2, not very expensive and easy to handle.

Of course other standard samples may be better in different conditions, but
knowing what you need and adapting your calibration to it is useful.

In the case of LaB6 I also find the first peak is too high in 2theta so you
end up with a lot of uncertainty on low angle profile width.

Best!
Leo

El lun, 26 abr 2021 a las 10:16, Jeremy Karl Cockcroft (<
jeremykarl at gmail.com>) escribió:

> Dear Huang,
> Just to add that, in our labs when working with Cu Ka1 radiation, we have
> used Y2O3 for a couple of decades as a standard for instrumental resolution
> (and hence peak-shape parameters). Typical PXRD patterns are shown in
> the following web pages, e.g.
> http://pd.chem.ucl.ac.uk/pdnn/unit1/accurate.htm (XY plot in 2theta)
> http://pd.chem.ucl.ac.uk/pdnn/inst2/eddcomp.htm (XY plot in 1/d)
> Y2O3 is excellent for generating lots of well-spaced peaks but it is
> absolutely *crucial* that it is sintered at high temperature for many days
> to improve its crystallinity. Even after sintering at 1200C for 5 days, our
> sample still showed slight broadening when Andrew Fitch measured it for me
> on the high-resolution PXRD beamline at ESRF (although it showed no
> broadening in the lab compared to other standards). However, it is not a
> good standard for checking low-angle peaks as the first peak with
> significant intensity is at approx. 20 degrees as shown in the patterns.
> Cheers,
> Jeremy Karl.
> p.s. Note that it is not very useful as a standard when working with Mo
> Ka1 radiation (as used on two of our lab PXRD diffractometers) due to
> severe fluorescence.
> ***************************************************************
> Dr Jeremy Karl Cockcroft
> Department of Chemistry
> (University College London)
> Christopher Ingold Laboratories
> 20 Gordon Street
> London WC1H 0AJ
> +44 (0) 20 7679 1004 (laboratory)
> j.k.cockcroft at ucl.ac.uk or jeremykarl at gmail.com
> http://img.chem.ucl.ac.uk/www/cockcroft/homepage.htm
> ***************************************************************
>
>
>
> On Mon, 26 Apr 2021 at 03:16, Huang Liu via GSAS-II <gsas-ii at aps.anl.gov>
> wrote:
>
>> Thank you very much for your suggestion.  We have Y2O3 in our lab. I will
>> try it. Thank you very much.
>>
>> Best regards,
>> Huang
>> ------------------------------
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>> *Subject:* GSAS-II Digest, Vol 303, Issue 1
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>> Today's Topics:
>>
>>    1. Re: Instrument parameters (Leopoldo Suescun)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sat, 24 Apr 2021 11:53:27 -0300
>> From: Leopoldo Suescun <leopoldo at fq.edu.uy>
>> To: "Toby, Brian H." <toby at anl.gov>
>> Cc: Huang Liu <huang.liu at utah.edu>, Huang Liu via GSAS-II
>>         <gsas-ii at aps.anl.gov>
>> Subject: Re: [GSAS-II] Instrument parameters
>> Message-ID:
>>         <CAAeV=
>> thDqvA0vfZ2a6zoen9tH34vVaG3Y7yPTy8CBnWW2M2_LA at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Hi Brian and Huang,
>> I use Y2O3 for this purpose. It is not very expensive and got a reasonable
>> amount of peaks at low angles. In order to minimize size and microstrain
>> effects, I fire pure Y2O3 for 3 days at 1200 ?C.
>> I hope it helps.
>> Leo
>>
>> El lun, 19 abr 2021 a las 23:59, Toby, Brian H. via GSAS-II (<
>> gsas-ii at aps.anl.gov>) escribi?:
>>
>> > Hi Huang,
>> >
>> >     First of all Si is not a good standard to use for instrument
>> > parameters. It has no peaks at low angle. LaB6 is a better choice. If
>> you
>> > do not have that, perhaps others seeing this can recommend something
>> > readily available with plenty of sharp peaks.
>> >
>> >     GSAS-II has no limits on the number of phases that can be read, but
>> > there was a bug with reading that particular  CIF. In it the element
>> types
>> > were specified as Ti0, Fe0 and O0 which GSAS-II could not process. I
>> have
>> > repaired this bug in version #4887.
>> >
>> > Brian
>> >
>> > On Apr 18, 2021, at 6:04 PM, Huang Liu via GSAS-II <gsas-ii at aps.anl.gov
>> >
>> > wrote:
>> >
>> > Hi,
>> >
>> > This is Huang Liu from the University of Utah. I am trying to use GSAS 2
>> > to do refinement on my data.
>> > 1. I try to get the instrument parameters according to the tutorial
>> >  (
>> >
>> https://subversion.xray.aps.anl.gov/pyGSAS/Tutorials/CWInstDemo/FindProfParamCW.htm
>> > ).
>> > But the U parameters that I get are always negative, and the Rwp is
>> above
>> > 10. I am using the data generated by*Rigaku mini flex 600 *by *using SRM
>> > Si 640d* as a standard sample for generating instrument profile
>> > parameters.   The attached file (Si-640d) is the original data.
>> > Could you please help me generate the instrument profile?  Thank you
>> very
>> > much.
>> > 2. I try to import Ti2Fe4O phase into the GSAS2, but I failed.
>> > Since this is the third phase that I want to import. May I ask is there
>> a
>> > phase quantities limit of import?
>> > If not, is there anything wrong with my CIF file (I downloaded it from
>> the
>> > COD website?
>> > Attached is the Ti2Fe4O cif card downloaded from COD website.
>> > I would be very grateful if you can help me. Looking forward to your
>> reply.
>> >
>> > Best regards,
>> > Huang Liu
>> >
>> <Si-640d.ras><Ti4Fe2O.cif>_______________________________________________
>> > GSAS-II mailing list
>> > GSAS-II at aps.anl.gov
>> > https://mailman.aps.anl.gov/mailman/listinfo/gsas-ii
>> >
>> >
>> > _______________________________________________
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>>
>>
>> --
>> #YoUsoTapabocas y mantengo #DFS
>>
>> Prof. Agr. Dr. Leopoldo Suescun
>> Cryssmat-Lab/DETEMA, Facultad de Qu?mica, Universidad de la Rep?blica.
>> e-mail: leopoldo at fq.edu.uy
>> Tel: (+598) 29290705
>> Fax: (+598) 29241906*
>> Mailing address:
>> Cryssmat-Lab./DETEMA
>> Facultad de Quimica
>> Av. Gral. Flores 2124
>> Montevideo 11800
>> Uruguay
>>
>> Seguime en/Follow me at ResearchGate
>> https://www.researchgate.net/profile/Leopoldo_Suescun
>>
>> ORC*ID*: https://orcid.org/0000-0002-7606-8074
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-- 
#YoUsoTapabocas y mantengo #DFS

Prof. Agr. Dr. Leopoldo Suescun
Cryssmat-Lab/DETEMA, Facultad de Química, Universidad de la República.
e-mail: leopoldo at fq.edu.uy
Tel: (+598) 29290705
Fax: (+598) 29241906*
Mailing address:
Cryssmat-Lab./DETEMA
Facultad de Quimica
Av. Gral. Flores 2124
Montevideo 11800
Uruguay

Seguime en/Follow me at ResearchGate
https://www.researchgate.net/profile/Leopoldo_Suescun

ORC*ID*: https://orcid.org/0000-0002-7606-8074
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