[Ifeffit] one more thing about atoms error

[Bruce Ravel]

Hey Carlo,

Upon further investigation, the root of the problem is in TkAtoms.
More specifically, it is when you have TkAtoms save an atoms.inp
file.  When you do, it sets all of the occupancies to 0 *and* puts
itself into a state where you cannot change the occupancies.  This, in
turn, leads to the problem computing the corrections.  This is quite
strange in that I don't remember changing anything in TkAtoms that
would have lead to this behavior.

The simplest solution seems to be not to use TkAtoms.  Artemis isn't
broken in the same way.  Saving the input file via "Theory->Write
special output->atoms" causes no such problem.  You can re-import that
atoms.inp file and have no problem.  Or, you could edit the atoms.inp
file remove all the 0's for occupancy.  Or, you could edit the
atoms.atp file to not write out the occupancy.  Many work-arounds!

So, the bugs that I need to fix:

1.  Whatever is causing the problem in TkAtoms (see P.S. below)
2.  Do some better error handling in the part of the code that
    computes corrections so that it does not choke on the occupancy
    problem
3.  I discovered a problem in the order of paths that are searched for
    atp files
4.  The atoms page in Artemis is very unhappy if you forget to select
    a central atom when entering data by hand

As I said, that's a pretty decent list for a single bug report!

B

P.S.  I can't remember if I mentioned this before, but I plan to
discontinue support for TkAtoms eventually.  I suspect that some might
complain about this, but I have my reasons.  I mention this so that no
one is surprised when the day come that I stop fixing bugs when they
crop up in TkAtoms.  That day ain't today, but it will be soon.

P.P.S.  In private email, you mentioned that you would rebuild your
debs with the modified feff.atp file.  That's your prerogative, but
the file isn't broken.  In my opinion, the best move would be to edit
your atoms.inp file, remove the occupancy column, and carry on.  The
second best move would be to edit the atoms.atp file to not write
out the occupancies since they are not used for anything  in Artemis.
Editing the feff.atp file is, I think, a distant third best option.

-- 
 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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