Giuseppe Piero Brandino gbrandino at gmail.com
Wed Nov 22 11:14:58 CET 2006

```Thank you sir  for the fast reply,

Giuseppe Brandino

On 11/21/06, Stefano Baroni <baroni at sissa.it> wrote:
>
>
>  On Nov 21, 2006, at 12:26 AM, Giuseppe Piero Brandino wrote:
>
>  Dear espresso user,
> i have some questions about the pp.x program.
> Asking the code to write the potential, for example
>
> plot_num=11=the V_bare + V_H potential,
>
> does it print the potential or the potential energy?
> I know that it prints it in Rydberg, so an energy.
>
>
>
> right
>
>  How do i get the potential? simply dividing by e
>
>
>
>
> right
>
>   or dividing by the total (ionic and electronic) charge density
> in each point?
>
>
>
> this is a bit confusing to me. why would you divide by the local charge
> density? an energy divided by a charge density makes a potential times a
> volume, which is not what you expect, and furthermore I am not aware of any
> sensible use of the resulting quantity.
>
>  Something else,
> is there a simple way to get the total charge density (electronic + ionic)
> from pp.x?
>
>
>
> The ionic *pseudo*charge density is ill-defined when the pseudopotential
> is non local (as it usually the case). On the other hand, the physical
> (all-electron) valence+core charge density is not simply the sum of the
> valence pseudo-charge+ionic charge. What would be needed here  is the sum of
> the all-electron ionic charge density + the valence charge density obtained
> from the reconstructed wave-functions. This is what is done the PAW
> formalism (see PE Bloechl, Phys. Rev. B 50, 17953 - 17979 (1994)). Work is
> in progress to implement PAW in Quantum Espresso. Meanwhile, there might be
> tools available to obtain a (more or less) quick-and-dirty recostruction of
> the charge, but others may be more appropriate than me to address this
> point.
>
>
> Stefano Baroni
>
>  ---
> Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
> [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)
>
> Please, if possible, don't  send me MS Word or PowerPoint attachments
> Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html
>
>
>
>
>
>
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