[Pw_forum] charge analysis

[Jure Varlec]

Trying Giussepe's advice on the system I am working on ATM, I could
only produce small differences between plot_num=0 and 17, and
negligible differences with increasing grid density. That would explain
why I haven't noticed any issues yet. However, it is clear that, should
I have to deal with a more problematic system, I would waste a lot of
time to realize there is a problem at all, and I would spend a lot of
foul language before finding a solution. So a big thank you to Axel,
Giuseppe and Tiana for your advice.

Best regards,
Jure

On Mon, 27 Jul 2015 15:34:13 +0200
Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it> wrote:

> Dear Jure and Axel
> Axel is right. A smooth charge density including core electrons
> yields best results, specially if the pseudopotential core region is
> somehow entangled with the assignment of a given set of grid points
> to the Bader's volume of a given atom. Notwithstanding (at least in
> my experience):
> 
> a) if you use PAW pseudopotentials you can extract a reconstructed
> and smooth all-electron charge density by using the plot_num=17
> option of pp.x, together with a *very dense* real space grid (2 or 3
> times the grid you find in the pw.x output). In this way you
> generally crunch reliable Bader's numbers.
> 
> b) the same holds for *reasonably hard* NC pseudopotentials, where
> any overlap between core regions and density minima is unlikely.
> 
> Remember then to perform a last scf calculation after, e.g., a
> standard "relax" calculation, using high values of nr1, nr2 and nr3
> (beware of memory usage...), before post-processing the charge
> density to produce the cube file.