Hi all, Here are the references to these papers:
Cheary RW, Coelho AA (1998a) Axial divergence in a conventional X-ray powder diffractometer. I. theoretical foundations. J. Appl. Cryst. 31:851-861 Cheary RW, Coelho AA (1998b) Axial divergence in a conventional X-ray powder diffractometer. II. Realization and evaluation in a fundamental-parameter profile fitting procedure. J. Appl. Cryst. 31:862-868 Cheary RW, Coelho AA (1992) A fundamental parameters approach to X-ray line-profile fitting. J. Appl. Cryst. 25:109-121 Patrick Mercier "Whitfield, Pamela" wrote: > Nandini > > If you're using standard Bragg-Brentano the true fundamental parameters > fitting from first principles will happily fit low angle asymmetry, as the > mathematical basis for it is well known (look for some papers that Alan > Coehlo and Bob Cheary did a while back, in J.Appl.Cryst I think). Axial > divergence is dealt with through modelling the effect of Soller slits, > source length, sample width and receiving slit length if my memory serves. > Monochromators, etc, also have effects, but these have to be determined > empirically. > > Pam > > Dr Pamela Whitfield CChem MRSC > Energy Materials Group > Institute for Chemical Process and Environmental Technology > Building M12 > National Research Council Canada > 1200 Montreal Road > Ottawa ON K1A 0R6 > CANADA > Tel: (613) 998 8462 Fax: (613) 991 2384 > Email: <mailto:[EMAIL PROTECTED]> > ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca > > -----Original Message----- > From: Nandini Devi Radhamonyamma [mailto:[EMAIL PROTECTED] > Sent: June 4, 2004 9:46 AM > To: [EMAIL PROTECTED] > > Thanks, Pam and Jon for the clarifications. > Again, does this approach take care of low angle peak > asymmetry better? > thanks, > > nandini > > --- "Whitfield, Pamela" > <[EMAIL PROTECTED]> wrote: > > Nandini > > > > The best people to reply on behalf of fundamental > > parameters would be Alan > > Coehlo or Arnt Kern. > > But until they do here goes.... > > > > The more general form is convolution-based profile > > fitting. This can be > > used for all peak profile types, whereas 'pure' > > fundamental parameters has > > only been inmplemented for the simple Bragg-Brentano > > case (no > > monochromators). Other geometries have to be > > empirically modelled using a > > standard and some sort of user-defined convolution > > on top of the source > > profile. Better fits can often be obtained using > > this type of fitting than > > the normal pseudo-Voigt or Pearson VII functions (in > > my experience at > > least). Where convolution-based fitting really > > comes into its own in in > > complex quantitative Rietveld analysis where the > > number of refined variables > > would become untenable for normal peak fitting. > > Using convolution-based > > fitting it is possible to cope with upwards of 10 > > phases with severe peak > > overlap and still get good results with good > > stability. For example, > > quantitative Rietveld analysis of cements is > > becoming routine. > > > > Pam > > > > Dr Pamela Whitfield CChem MRSC > > Energy Materials Group > > Institute for Chemical Process and Environmental > > Technology > > Building M12 > > National Research Council Canada > > 1200 Montreal Road > > Ottawa ON K1A 0R6 > > CANADA > > Tel: (613) 998 8462 Fax: (613) 991 2384 > > Email: <mailto:[EMAIL PROTECTED]> > > ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca > > > > > > -----Original Message----- > > From: Nandini Devi Radhamonyamma > > [mailto:[EMAIL PROTECTED] > > Sent: June 4, 2004 6:42 AM > > To: [EMAIL PROTECTED] > > > > > > Dear All, > > > > > > Is the fundamental parameter approach better than > > mathematical approach used in most of the Rietveld > > refinement programs? Does that mean programs which > > use > > that approach are better? Any suggestions? > > > > Nandini > > > > > > > > > > __________________________________ > > Do you Yahoo!? > > Friends. Fun. Try the all-new Yahoo! Messenger. > > http://messenger.yahoo.com/ > > > > __________________________________ > Do you Yahoo!? > Friends. Fun. Try the all-new Yahoo! Messenger. > http://messenger.yahoo.com/ -- Dr. Patrick H.J. Mercier, P.Phys., ing. jr Research Associate Department of Physics University of Ottawa 150 Louis Pasteur Ottawa, Ontario, Canada K1N 6N5 Telephone: (613)562-5800 extension 6743 Fax: (613)562-5190 E-mail: [EMAIL PROTECTED]
