A 11:36 27/11/98 +0100, vous avez �crit:
>Dr Sue Kesson wrote:
>>..... time for another global humiliation.....
>>
>>Is something wrong if the value for NA (pseudo voigt) exceeds unity?
>
>Nothing necessarily wrong.
>This may indicate a bimodal distribution of profile-broadening effects.
>See : R.A. Young & A. Sakthivel, J. Appl. Cryst. 21 (1988) 416-425.
>(Ray is too moderate for a self-citation..:-).
>
Such bimodal (or polymodal !) distributions of sizes or strains responsible
for super-lorentzian shapes can be fitted if the eta value becomes too large :
- by introducing two completely constrained phases in your Rietveld
refinement (one with broad and the other with narrow profile) (see for
example J.-M. Joubert et al., J. Appl. Crystallogr. 31 (1998) 327-332).
- by using the program WINFIT by S. Krumm
(http://www.geol.uni-erlangen.de/software/winsoft.html) (see also proc.
EPDIC IV, S. Krumm, Mat. Science Forum,228-231 (1996) 183-188).
Regards.
---------------------------------------------------------------
Jean-Marc Joubert
Laboratoire de Chimie Metallurgique des Terres Rares
CNRS - UPR 209
2-8 rue Henri DUNANT,
94320 THIAIS CEDEX - FRANCE
Phone: 33 (0)1 49 78 12 11
Fax: 33 (0)1 49 78 12 03
Email: [EMAIL PROTECTED]
