pseudopotential for charged atoms ?

[Matthias Krack]

Dear Valerio,

you are right. Basically, you need only to change the electronic
configuration in atom.dat to generate the proper all-electron
reference. Usually, the PP parameters for the neutral atom are a good
initial guess. Just take care that the number of electrons is
matching. The GTH PPs show a quite nice transferability. To my
experience there is no need (and no gain) to employ such
pseudopotential variants adapted to or tuned for the specific
application. The semi-core PP of Ni should work just fine.

cheers,

Matthias

On Dec 15, 12:50 pm, "Valerio Bellini" <valerio... at unimore.it>
wrote:
> Dear all,
>
> I am a REALLY beginner in the business of pseudopotential generation, so
> forgive me if the question is trivial.
> Suppose I want to create a GTH pseudo for an element (e.g. Ni), for which
> I know that in the system I want to study it is found in a well defined
> valence state (e.g. Ni2+ as in NiO)..
> My question is: is it possible to create a pseudo that replicates the WFs of
> a Ni2+ atom? I know that in principle pseudo might be transferable, but
> it might be that checking the transferability error, as explained in the
> README file of the program pseudo.x, the error are too big. Adding
> semicore stated might resolve this situation or not, depending on the
> elements and on the orbitals of interest.. I presume.
> If it is possible, do I just need to modify the occupation in the atom.dat
> file for the creation of the reference all-electron WFs, and start the
> fitting of the parameters, as in a standard neutral atom or is there
> something else I should take care?
> I guess that the parameters in psp.par relative to a non-charged
> calculation are not good a starting point, since if I plot the WFs for the
> Ni2+ atom empty orbitals have WFs much more contracted towards the nucleus
> due to the two holes (3d8 4s0 instead of 3d8 4s2), so that I will need to
> start from scratch. Is is true?
> Actually the Ni2+ is just an example, I am interested in several other
> transition metals or even lanthanide atoms.
>
> cheers,
> Valerio