[GSAS-II] Ask: Micro strain and Crystallite size Determination

[Michael Gaultois]

Good evening,

I tried experimenting with the crystallite size and microstrain features in
GSAS-2, and it seems to work pretty well. I used the ESRF BM16 dataset
provided in the size/strain
round-robin<http://www.ccp14.ac.uk/ccp/web-mirrors/balzar/div853/balzar/s-s_rr.htm#Round-Robin%20materials>sponsored
by Davor Balzar at NIST and UC Boulder.

*Crystallite size:*
The domain size is believed to be 17.4 +/-0.1 nm
The average volume-weighted domain size determined by the participants was
22.6 +/-0.9 nm.
My average volume-weighted domain size determined was 24 nm. (no error
given in the .lst file)

*Strain:*
The expected strain is ~0.
My determined microstrain was -1.9. (this is ~0)

--
The limitation, like any refinement, is that your answer depends on your
initial guess. Even with other programs, there was mention in the
discussion of the round robin that if your strain comes out high, your
crystallite size becomes erroneously large to compensate. I've also noticed
in some of my other refinements that I have to nudge the crystallite size
to something close before it refines properly. (Otherwise it just remains
roughly constant.) I hope this is helpful.

Warm regards,
Mike

--
Michael Gaultois
PhD Candidate *candidate*

Seshadri Group <http://www.mrl.ucsb.edu/~seshadri/>

Materials Research Laboratory 5121
University of California
Santa Barbara CA 93106-5121

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On 13 January 2013 20:01, maykel manawan <maykeltem at yahoo.com> wrote:

> Dear all,
>
>
> On page 162-164 GSAS manual, there is an explanation about the strain and
> particle size.
>
> Do they work the same in GSAS-II ???
>
> What condition in sample and or refinement to be satisfied to get the
> trust-able result ???
>
> And what is the limitation ???
>
>
>
>
>
>
> Best regards,
>
>
>
> Maykel Manawan
> Material Science Study
> Postgraduate Program of Faculty of Mathematics and Natural Sciences
> University of Indonesia,Depok 16424 Indonesia
> Tel: +6221-7872610 / Fax: +6221- 2863441
> email: maykel.t01 at ui.ac.id
>
>
>
>
>
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