[CP2K:1467] Re: molecular dipoles of charged molecules

[Laino Teodoro]

> hmmmm.... the organization of this part of the input is a  
> bitconfusing.
>
> i would have either expected that you move them to the
> CP2K_INPUT / FORCE_EVAL / DFT / PRINT / LOCALIZATION / LOCALIZE /
> PRINT
> block where the other wannier center related output is found or
> - which makes even more sense to me - move those subsections
> directly into LOCALIZATION and merge LOCALIZATION%LOCALIZE
> into LOCALIZATION.

Well.. it has a sense how it is organized at the moment.
In fact,  wannier centers (which are controlled by the LOCALIZE  
section  and the printing of the WANNIER* is controlled by that section)
are used in the LOCALIZATION section to compute/print properties  
(MOLECULAR_DIPOLES,  TOTAL_DIPOLE and MOLECULAR STATES) that depend  
on the WANNIER centers..
With the today re-organization, the real print keys are  
MOLECULAR_DIPOLES, TOTALE_DIPOLE, MOLECULAR_STATES,
(hopefully the manual online should be soon updated).
LOCALIZATION is therefore just a container for properties computed  
using wannier centers  (controlled by LOCALIZE).

WANNIER centers are also used in other sections, like LINRES:
http://cp2k.berlios.de/manual/CP2K_INPUT/FORCE_EVAL/PROPERTIES/ 
LINRES.html

that's why everything connected with the printing of wannier  
functions (centers, spread, cubes) must
be in the LOCALIZE%PRINT section, and there you don't want to put for  
example dipoles or molecular_states.
to me, it makes sense how it is organized..

> the documentation there is very terse. i understand this section
> as computing properties of the "total" system, right?
Absolutely right.. MOMENTS is always referred to the total system..

> well, that makes the resulting dipole depend on the shape of the  
> molecule.
> it is not a big deal for most molecules, but it is for the kind of  
> molecule
> that i am currently looking into, which is a small organic cation  
> that is
> mostly flat and picks up a dipole moment from bending and being  
> polarized
> from solvate molecules.

well.. even with the center of charge or center of mass the dipole  
will always depend
on the shape of the molecule.. it's unavoidable..
maybe the center of charge or of mass behaves better.. but anyway..  
as you said in the
first message the problem is ill-defined..

> i'll look into it. i don't really need that kind of output, since i  
> have
> an equivalent implementation with sufficient flexibility already  
> integrated
> into VMD (Extensions->Visualization->Dipole Moment Watcher), but i was
> a bit surprised by the discrepancies and wanted to check with the  
> folks
> here whether this was intentional or accidental.

I would say more laziness... ;-)
Teo