how to get the "total" electron density

[Axel]

hi!

thanks for the answers. this is very encouraging.

On Mar 13, 6:12 am, Fawzi Mohamed <fa... at gmx.ch> wrote:
> On Mar 13, 2008, at 9:23 AM, Matthias wrote:
>
>
>
> > Hi Axel,
>
> > indeed, the all-electron density is available with GAPW, but only in
> > Fourier space as it is needed for the calculation of the X-ray
> > diffraction spectrum. In principle one could perform a back
> > transformation to real space using FFT and print it as a cube file.

ok. can you give me a few hints on which code specifically
to look at, so that i can try hacking it together?

> > However, for numerical reasons you would apply in this way a low pass
> > filter to the all-electron density and thus you would not obtain the
> > true all-electron density in real space.
>
> actually I think that this is the correct thing to do, we should
> maybe do something like this also instead of the stride (or at least
> do some mean).

yep. visualisation doesn't really need much accuracy, but analysis
does and preserving the integral of the property would be very helpful
in the particularl analysis that i have in mind.

an alternate option would be to incorporate the analysis directly
into cp2k (i'm currently thinking of the code from
http://theory.cm.utexas.edu/bader/ which looks like it
could be merged with rather moderate effort) and thus at least
avoid the issue of having to read and write huge formatted files.

cheers,
   axel.

> direct collocation of the gaussians (and also stride as now done) do
> not conserve the total density when the cutoff is not high enough
> (basically always with GAPW).
>
> ciao
> Fawzi
>
>
>
> > cheers,
>
> > Matthias
>
> > On Mar 13, 2:30 am, Axel <akoh... at gmail.com> wrote:
> >> hi everybody,
>
> >> would there be a way to get the total _electron_ density from
>
> >> quickstep GPW/GAPW calculations?
>
> >> i actually found a flag to output a 'total density', but that turned
> >> out to be the valence electron
> >> density plus the (smeared out?) core charge density, with the odd
> >> side
> >> effect that the cores were
> >> negative and the electrons positive. i guess it does not really
> >> matter, but...
>
> >> for all-electron GAPW calculations, this information should - in
> >> principle - be available.
> >> the question is, would it be much effort to put it into a cube file?
>
> >> for pseudopotential based calculations, be it GPW or GAPW one could
> >> just use the
> >> density that was "removed" during pseudopotential generation.
>
> >> any comments or suggestions would be highly appreciated.
>
> >> cheers,
> >>    axel.