[Ifeffit] Generating single scattering paths in Artemis

[John J. Rehr]

One of the nice things about FEFF3 is that single scattering calculations
were pretty well automated. Since then it's been possible, but not that
easy. The OVERLAP cards, in particular were hacked together to get
reasonable potentials, but even I don't find them friendly.

It seems to me that one could/should arrange the defaults in FEFF>3 to 
permit a FEFF3 type calculation, e.g., with specification of coordination
approx number near neighbor distance (that could be estimated by default too)
and backscatterer type only.

Since Artemis calls FEFF6, perhaps (?) such defaults could be built into
a special call. That seems to me to be what a number of people in the list are
asking for.

  John Rehr