[Pw_forum] About background charge
Lorenzo Paulatto
paulatto at sissa.it
Tue Jul 7 09:18:31 CEST 2009
On Tue, July 7, 2009 08:27, oulihui666 wrote:
> Thus, I'd like to ask if PWSCF can do calculations that vacuum layer do
> not fill backgrount charges ?
The system is not really filled with background charges, what is really
done is actively set the G=0 component of V to zero. In this way the
average value of the potential over the unit cell is zero, and everything
works fine (if you can afford a cell big enough to suppress periodic image
interaction)
> I have checked the manual and original pipemails, but didn't find many
> topics on background charges.
There are a few, e.g.
<http://www.democritos.it/pipermail/pw_forum/2005-April/002379.html>
> However,I found many discussions on EXTERNAL POTENTIAL which makes it
> possible to add an external electrostatic field.
> If possible, how ?
Have a look at the documentation, Doc/INPUT_PW.html; there are two ways to
do it: using a sawtootk potential or using the modern theory of
polarization (Berry phase); the latter is only implemented for insulators.
>
> Many thanks.
best regards
--
Lorenzo Paulatto
SISSA & DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www: http://people.sissa.it/~paulatto/
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