misleading warning message

[Bruce Ravel <ravel@phys.washington.edu>]

Hi,

FEFF8 currently is fond of telling me the following when I am
computing phase shifts:

  WARNING: increase ltot in dim.h for more accuracy at high k to  27

I suggest that this message could be restated to be more informative
and less alarming to the user.

I suspect that what is actually meant by this is that the calculation
is only accurate up to a certain value of k, which I will call k_acc.
Beyond k_acc, the calculation is suspect because the basis used in the
calculation does not consider enough angular momentum states.

If I understand this error message, FEFF is telling me that I need to
set ltot to 27 in dim.h and recompile the code if I want FEFF to be
accurate beyond k_acc.

What I suggest is that this message be changed to something like the
following:

  This phase shift calculation is accurate to k=k_acc.
  See section X.XX of the FEFF document for details on how to increase
  the accurate range.

Of course, "k_acc" should be replaced by the right number.  I would
suggest the integer part of the calculated value.

My suggestion is better for the user because it tells him how the
calculation is good, rather than nebulously warning him that the
calculation might be bad.  My message would be comforting.  The
current message is scary.  It also directs the user to the document
where the issues with ltot, dim.h, and recompiling can be fully
explained.

Regards,
B


-- 
 Bruce Ravel  ----------------------------------- ravel@phys.washington.edu
 U.S. Naval Research Laboratory, Code 6134          phone: (1) 202 767 5947
 Washington DC 20375, USA                             fax: (1) 202 767 1697

 NRL Synchrotron Radiation Consortium (NRL-SRC)
 Beamlines X11a, X11b, X23b, X24c, U4b
 National Synchrotron Light Source
 Brookhaven National Laboratory, Upton, NY 11973

 My homepage:    http://feff.phys.washington.edu/~ravel 
 EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/