[Pw_forum] How to simulate cation H+ without electron or Li+ with only two electrons

[Hoi-land Sit]

Dear Vega,

I am not sure if i understand well your question. But in the work 
mentioned by Lorenzo, we introduced a penalty functional to control the
ionization state of an ion. It is done by forcing a desired occupation 
number on the ion when the K-S orbitals are projected on the atomic 
orbitals. This technique was used to study electron transfer reactions, in 
particular to calculate the energy gap between diabatic states. In such 
calculations, the system is forced out of its DFT ground state. at this 
moment, we are working to incorporate this part of the code to be 
available for download.

Best,

Patrick Sit
Postdoctoral Associate
Center for Molecular Modeling
University of Pennsylvania

On Tue, 15 Jul 2008, Lorenzo Paulatto wrote:

>
> On Mar, Luglio 15, 2008 12:11, vega lew wrote:
>>  Si with 14 electrons.
>>  Cations lose some electrons such as H+ without any electrons and Li with
>>  only 2 electrons.
>
> You cannot force it: you can remove one electron from the system, than if
> the ground state (in the adopted theoretical frame) has a ionized H or Li
> it shall be found at convergence.
>
> Actually Sit, Cococcioni and Marzari (PRL97, 028303) use some sort of
> trick to force a certain ionization state. I don't know if the code is
> available (but you can certainly ask them).
>
>
>>  Do you think pseudopotential with plane wave basis sets DFT calculation
>>  is suitable for this mater?
>
> I have no idea, certainly it may take a bit of effort to converge an
> isolated charged system wrt the size of the unit cell.
>
> bye
>
>