counter charge

Jun chen... at
Fri Apr 17 14:55:29 UTC 2009


I thought I can put some classical point charges (fractional) in a
cell using Quickstep. But I can't find the way out.
Is that possible in QS? I guess QM/MM can do this. Since I have no
experience on it, I would like not to go that far.
Many thanks in advance.


On Apr 9, 3:08 pm, Teodoro Laino <teodor... at> wrote:
> Just a remark:
> of course the energy of an isolated charged system is well defined.
> It is not defined in case of a periodic charged system (without
> considering the
> neutralizing background charge).
> cheers,
> Teo
> Teodoro Laino wrote:
> > Dear Jun,
> > Just to avoid confusion, the neutralizing background charge is not
> > something  manually added  in CP2K because
> > we don't like to have charged systems.. It comes out of the box from
> > the EWALD summations and there's
> > nothing you can do to avoid it (the energy of a charged system would
> > terribly diverge!!!)...
> > unless... unless your system is not charged..
> > The answer to your question is : no, it is not possible. And even if
> > it would be possible, it may end up in problematic
> > issues.
> > Think about putting counterions, instead, in your simulation if you
> > don't like to have charged systems.
> > Teo
> > Jun wrote:
> >> Hi all,
> >> I want to calculate a system with a net charge. I know cp2k will
> >> automatically apply a homogeneous neutralizing background charge with
> >> opposite sign in the simulation cell. Is it possible in cp2k to define
> >> an area with any shape (e.g. sheet or slab) in which the counter
> >> charge is evenly dispersed? Or any other way to do this?
> >> Many thanks, and happy Easter holiday.
> >> Jun

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