[CP2K:2427] Wannier centers and molecular dipoles

Teodoro Laino teodor... at gmail.com
Fri Nov 27 16:32:21 UTC 2009

You can:

1) CENTER your system in 0. 0. 0.
             CENTER_POINT 0. 0. 0.

2) Use MT (which is translational invariant) instead of WAVELET (which 
forces the system to be between 0 and L) as POISSON_SOLVER.

I'm quite sure (ready to be contradicted) that modifying your input 
consistently with points (1) and (2) you should get the right answer.
A general fix for that in the case of periodic none is quite improbable 
since Wannier are fully consistent (in cp2k of course) only if you work 
in PBC for several boring technical reasons.

Moreover keep in mind that since the molecules may not be necessarily 
neutral the molecular dipoles may change on the basis of the reference 
point (this probably is the case for the one you said has two water 
molecules close to each other).


Ondrej Marsalek wrote:
> Dear all,
> I would like to get the Wannier centers and molecular dipoles in a
> calculation in open boundary conditions. I have found two problems. I
> attach two test calculations, together with the output on my machine.
> They have two water molecules and differ only by the position of one
> of them - in the "together" case they are both in the first octant,
> while in the "separate" case they are more spread out.
> 1) The Wannier centers are wrapped into the cell from -L/2 to L/2.
> This is a bother for display, but can in principle be resolved in
> post-processing. Unfortunately, it looks like these positions are also
> used for the assignment to molecules and the calculation of charges
> and dipoles. The problem of course does not demonstrate if all the
> centers fall into the first octant. This is the relevant part of the
> output from the two calculations:
>                            # molecule nr, charge, dipole vector, dipole (Debye)
>      1    0.000000 -184.870480 -135.671636 -201.729105  305.415322
>      2    0.000000 -132.712114 -197.946467 -134.405404  273.605778
>                            # molecule nr, charge, dipole vector, dipole (Debye)
>      1    0.000000    0.000000    0.000000    0.000000    0.000000
>      2   -8.000000  129.208809  111.938778  101.509883  198.820177
> 2) Even when the centers are in the right places, the dipoles above do
> not look right.
> Can someone please confirm that they get the same results? If so, I
> would like to ask for a fix, if possible.
> Thanks,
> Ondrej
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