Re: Rietveld assymetry parameter

L. Cranswick ( L.M.D.Cranswick@dl.ac.uk )
Fri, 23 Jan 1998 08:49:30 +0000 (GMT)

Warning - minor web self-citation follows -

From a pointer at List of PC (and Mac) Rietveld and Related Powder
Diffraction Software

http://www.unige.ch/crystal/stxnews/riet/faq/progs/riet-pc.htm

Under the option of: Rietveld Related Code and Algorithms

Source code from Finger et.al in various languages (C, Fortran,
Pascal) at:
ftp://cryst.ciw.edu/profile/

Lachlan.

PS: If anyone knows the location of other algorithms for Rietveld
and related areas on the internet - or which could be put on
the internet (There is web space as part of the Collaborative
Computational Project Number 14 (CCP14) for Single crystal
and Powder Diffraction - if code volunteers don't have
their own web-site) - please feel free to email me.

>
> In short, don't use that function it does not work well for even minor levels
> of assymetry. The assymetry function to use is the Finger-Cox-Jephcoat equation
> [L.W. Finger, D.E. Cox & A.P. Jephcoat (1994) J. Appl. Cryst.,27,892-900.].
> That function has three input values, (sample height, detector height &
> instrument radius) all of which you should know, and thus has no terms to fit.
> It works well. Don't bother with split-Pearson functions either. They have no
> physical basis.
>
> My guess is that if you send an e-mail message to Larry Finger
> (finger@geolab.ciw.edu) he will send you a subroutine in the computer language
> of your choice. Well, maybe not COBOL.
>
> Brian
>
> --
> ********************************************************************
> Brian H. Toby, Ph.D. Leader, Crystallography Team
> Brian.Toby@NIST.gov NIST Center for Neutron Research E151/235
> voice: 301-975-4297 National Institute of Standards & Technology
> FAX: 301-921-9847 Gaithersburg, MD 20899
> ********************************************************************
> 

-- Lachlan M. D. CranswickCCP14 for Single Crystal and Powder DiffractionDaresbury Laboratory, Warrington, WA4 4AD U.KTel: +44-1925-603703  Fax: +44-1925-603173  Room C14E-mail: l.cranswick@dl.ac.uk

Personal Crystallographic WWW:                    http://www.unige.ch/crystal/stxnews/stx/volnteer.htmCommission on Powder Diffraction, Quantitative Phase Analysis Round Robin:                                   http://www.dl.ac.uk/SRS/XRD/IUCR/QARR/Society of Crystallogaphers in Australia (SCA):   http://www.sca.asn.au/Australasian Web Publishers Association: (AWPA):  http://www.awpa.asn.au/Australian X-ray Analytical Association (AXAA):                                   http://www.latrobe.edu.au/www/axaa/