Thank you for your clarifying 'protest' and for bringing up the fact,
apparently unknown to all too many, that there IS a record and that it is
relevant.
R. A. Young
At 06:16 PM 6/24/98 +0100, you wrote:
>Dear All,
>
>I must protest on the concept of a "new" fundamental parameter approach in
>Profile Analysis of Powder Data. As I have already remarked, the U,V,W was
>never meant to be empirical in the context it was developed for (Cagliotti,
>Paoletti & Ricci, Nucl. Intrum. V3, (1958) pp. 223-228). A "fundamental"
>correction for axial divergence was developed 15 years ago (B. Van Laar and
>W. B. Yelon, J. Appl. Cryst. 17, 47 (1984)) and later updated (L. W. Finger,
>D. E. Cox, and A. P. Jephcoat, J. Appl. Cryst. 27, 892 (1994)). People at
>central facilities have always tried to understand their instruments in a
>fundamental way, with the due mathematical appoximations. If this is not
>the case for lab x-ray users, this approach may be new for them, but I don't
>think this justifies the frasing used in the satellite meeting title. If
>somebody suggested to combine Rietveld with MC ray-tracing, this may be
>new, but I don't think we are there yet (not, perhaps, we need to).
>
>By the way, the distinction between a mathematical approximation and an
>empirical formula is the following: in the first case, the mathematical
>functions describing the physical phenomenon result from a series of
>approximations of more complex formulas (in other words, there is no
>reference to experimental data). In the second case, the functions are
>chosen only on the ground that they fit the data (in other words, there is
>no analysis of the physical process itself).
>
>Paolo
>
>
>Dr. Paolo G. Radaelli
>ISIS Facility
>Rutherford Appleton Laboratory, Bldg. R3
>Chilton, Didcot
>Oxon. OX11 0QX
>United Kingdom
>
>Phone : (+44) 1235-44 6290
>FAX : (+44) 1235-44 5642
>e-mail: P.G.Radaelli@rl.ac.uk
> pgr@isise.rl.ac.uk
>
>
>
>
R. A. Young, Professor Emeritus
School of Physics
Georgia Institute of Technology
Atlanta, GA 30332 USA
Tel: 404-894-5208
e-mail: r.young@physics.gatech.edu