Dear Leonid:
Eventhough I am subcribed to the Rietveld list, I have been only a "reader"
so to speak.
I would appreciate it very much if you could post my following comments on Rietveld
readers list.
Thanks very much for you cooperation in advance.
Koray
The Chapter by Delhez in the "Rietveld Method" ( Ray Young ed.), a
comprehensive tretament
on crystallite size
and strain broadening phenomena is given. In there, the formulas relating FWMH to
integral breadths
for all the major
peak shape functions are presented. After proper modelling of the peak profiles, i.e.
extraction of
Gaussian and Lorentzian contributions to FWHM, one can determine the corresponding
integral breadths
with relative ease. Delhez's chapter
also explains how to calculate size and strain using the integral breadths.
I would also recommend to compare the size as determined by x-ray
diffractometry to the
physical size of the crystallites observed under the SEM. That'll disclose useful
information
(however qualitative) about the "state of perfection" of crystallites. Thereby, you
can, to a
certain extent, justify wheather there really is microstrain in the crystallite or
not.
Best regards,
Koray
E. Koray Akdogan, Ph.D.
Postdoctoral Research Associate
Center for Ceramic Research
Rutgers University
607 Taylor Road
Piscataway, NJ 08854-8065
Voice: (732)-445 5614
Fax: (732)-445 5577
E-mail: [EMAIL PROTECTED]
----Original Message-----
From: Leonid Solovyov <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Date: Thursday, November 30, 2000 12:10 AM
Subject: Re: more questions about the Scherrer formula
>>When I use the pseudo-Voigt function corrected by
>Thompson-CoX-Hastings
>>in the Rietveld software the calculations for size and strain are
>make
>>with fwhm instead
>>integral breadth, is this a mistake? or can I calculate the
>>values for integral breadth and then apply to the formulas for
>>size/strain?
>
>The exact way of calculating the size-strain parameters must depend on
>the Rietveld software you use (it should be written in the manual).
>The use of FWHM is Ok if it is properly converted to the integral
>breadth in accordance with the peak shape. If it is not converted, you
>may do it manually to use in the Sherrer formula.
>
>I also hope that the Size-Strain Round Robin results will suggest the
>best way of obtaining the size-strain parameters from Rietveld
>refinement.
>
>Best,
>Leonid Solovyov
>
>
>__________________________________________________
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