[Pw_forum] Image charge interaction

Ilya Ryabinkin igryabinkin at gmail.com
Tue Sep 13 15:44:42 CEST 2016


> If I understand this correctly, it seems a less satisfactory answer that
just having the uniform jellium background?

No. In particular, I have Cl- species in my system, but there is no
way in common GGAs to keep an electron on chlorine -- due to self
interaction the electron is too weakly bound (if any) to Cl and DFT
gives a completely wrong, de-localized solution for an extra electron.
Neutralizing background will simply eat up the field of this
delocalized electron and I'll be simulating a system which resembles
more a *neutral* Cl atom on a slab rather than an anion.
One of the possible ways to work around -- is to devise a
pseudopotential for Cl with the configuration [He] 2s^2 2p^5 3s^2
3p^6, which has a hole in 2p and an extra electron in 3p, then "bury"
the hole inside a pseudopotential... This solution, however, leads to
the apparent lack of charge-image interaction since the resulting
pseudoatom is neutral (in fact, it looks like Ar).

> 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

I wish it could be true... but not for the common DFA-s

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

Yes. I'm wondering if some one already did this. I can do it myself,
but for the sake of not re-inventing the wheel...


On Tue, Sep 13, 2016 at 6:26 AM, Lorenzo Paulatto
<lorenzo.paulatto at impmc.upmc.fr> wrote:
> Hello,
> it is not too clear to me what you need, but is something like this: http://
> journals.aps.org/prb/abstract/10.1103/PhysRevB.89.245406 ?
> It is implemented in the upcoming version 6.0 of QE,
> The feature is still disabled in the downloadable beta versione, but it is
> enabled in the last daily snapshots at http://qe-forge.org/snapshots/ (no
> guarantee anything works).
> hth
> On Monday, 12 September 2016 18:13:25 CEST 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. However, the image-charge interaction is clearly
>> absent and we would like to bring it back.
>> Did anyone bother him/herslef to implement is in QE? I know VASP has
>> this capability, but it is out of scope.
>> Thanks in advance,
>> I.
> --
> Dr. Lorenzo Paulatto
> IdR @ IMPMC -- CNRS & Université Paris 6
> +33 (0)1 44 275 084 / skype: paulatz
> http://www.impmc.upmc.fr/~paulatto/
> 23-24/4é16 Boîte courrier 115,
> 4 place Jussieu 75252 Paris Cédex 05
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                    Ilya Ryabinkin
                 Postdoctoral Scholar
          Physical and Environmental Sciences
           University of Toronto Scarborough

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