[Pw_forum] Image charge interaction

[Nicola Marzari]

On 13/09/2016 00:13, Ilya Ryabinkin wrote:
> Dear colleagues:
> I am simulating dynamics of a charged particle on a metallic slab. To
> avoid difficulties with Coulomb energy of a charged cell, we use a
> core-hole trick to introduce a compensatory positive charge directly
> into a particle.

If I understand this correctly, it seems a less satisfactory answer that
just having the uniform jellium background? Also note that in the limit
where your slab is very large, the state of charge of your particle
will be determined by the physics - i.e. the xc functional will decide
how much charge should sit on the particle

> However, the image-charge interaction is clearly
> absent and we would like to bring it back.

Well, that is a challenge in DFT in general. There are some
old papers by Rex Godby, I think, on the topic.

> Did anyone bother him/herslef to implement is in QE? I know VASP has
> this capability, but it is out of scope.

Which capability? Adding an empirical extra term in the forces for
the charge?

Anyhow, if your particle is sitting on the slab there is not much
that you can do that is meaningful, I think (happy to be proved wrong!)
more than using whatever xc you feel it's best, and discovering a posteriori
what charge sits on the particle.
	
				nicola


-- 
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Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project