Dear Bruce,
thank you very much for your quick and thorough answer.
I used to do I/V-LEED to do structural characterization of surfaces and
there it was pretty common to get stuck in local minima. So my fear was
that this negative R-factor corresponds to a local minimum and that
there is actu
Felix,
When you fit your EXAFS data using Artemis + Ifeffit or Larch, you are
using a Levenberg-Marquardt non-llinear, steepest descent algorithm. The
fit does kn ow anything /at all/ about what you are trying to do. It
doesn't know what a sensible value for sigma^2 or any other parameter
is.
