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