Some minor issues

[Ondrej Marsalek]

Hi everyone,

I have some minor issues with CP2K. Nothing too bad, but perhaps someone
would be interested.

1) In the manual, in the section

   CP2K_INPUT / FORCE_EVAL / DFT / XC / VDW_POTENTIAL / PAIR_POTENTIAL

   it says for the ATOMPARM keyword: "This required keyword can be
   repeated and it expects a list of words." However, a simulation runs
   just fine with defaults without a single ATOMPARM keyword.

2) Manual again, section

   CP2K_INPUT / FORCE_EVAL / DFT / QS

   EXTRAPOLATION_ORDER: "Order for the PS extrapolation..."

   However, the setting is also relevant for the ASPC extrapolation.
   While this is strictly speaking also PS extrapolation (if I
   understand it correctly), it would probably be more clear if it
   referred directly to the EXTRAPOLATION setting (and therefore
   mentioned PS and ASPC).

3) Ghost atoms. It seems strange to me that you have to specify a
   pseudopotential and chemical element for a ghost atom. It
   specifically says at the GHOST keyword:

   "This keyword makes all atoms of this kind ghost atoms, i.e. without
   pseudo or nuclear charge.Useful to just have the basis set at that
   position (BSSE calculations),or to have a non-interacting particle
   with BASIS_SET NONE"

   So whatever you specify for pseudo and element gets (hopefully)
   ignored.  A somewhat bigger annoyance is ghost atoms seem to have a
   dispersion correction by default. Is this really the case? I
   certainly had to resort to the following ugly hack: specify an
   element that is not present in my system for the ghost atoms and then
   set the dispersion parameters to zero for that element (using
   ATOMPARM). It seems to work, but it is not pretty.

If any of the developers find this relevant, good. If any decide to
change stuff, great and thanks in advance. I am especially interested in
point 3), 1) and 2) are just details, but maybe useful for total
newcomers.

Best,
Ondrej