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 TeamBrian.Toby@NIST.gov NIST Center for Neutron Research E151/235voice: 301-975-4297 National Institute of Standards & TechnologyFAX: 301-921-9847 Gaithersburg, MD 20899********************************************************************