[CP2K:1459] molecular dipoles of charged molecules

[Laino Teodoro]

Ciao Axel,

I checked carefully the part of the code connected with the  
calculation of the dipoles (both total and for each molecule)
when using the wannier centers, i.e.:

DFT%PRINT%LOCALIZATION%MOLECULAR_DIPOLES
DFT%PRINT%LOCALIZATION%TOTAL_DIPOLE

While for MOLECULAR_DIPOLES they are always computed w.r.t the  
position of the first atom in the molecule,
the TOTAL_DIPOLE was (as you said) totally position dependent.  
Moreover, as I mentioned, it was absolutely not
related to the other possible way of computing dipoles: DFT%PRINT% 
MOMENTS

Therefore:
-) MOLECULAR_DIPOLES and TOTAL_DIPOLE are now print_key sections  
inside localization.
-) both sections have the same possible parameters as MOMENTS, i.e.:  
PERIODIC (if the dipole should be
    computed with the berry phase or not), REFERENCE and  
REFERENCE_POINT.
-) While these keywords are fully implemented for the TOTAL_DIPOLE  
section, they are not for MOLECULAR_DIPOLES
    since I think the convention used (i.e. to compute the dipole  
w.r.t. the first atom in the molecule) is already quite good.
    In case somebody will really need it, the implementation is quite  
straightforward..

Hope this solves your issue.
Teo

On 19 Oct 2008, at 03:32, Axel wrote:

>
> hi,
>
> this is a bit of a badly conditioned problem, but i noticed
> that the molecular dipole value computed for charged molecules
> does not take out any net charge and thus makes the resulting
> dipole strongly position dependent, and thus practically useless.
>
> i've met the same problem while writing a visualization tool for
> VMD and ultimately decided to remove the total charge at the
> center of the molecule to retain position independent results
> (and visualizations).
>
> are there any opinions on this matter?
> or even examples for where the current
> implementation is useful.
>
> thanks,
>     axel.
>
> >