[QE-users] Energy for Cells of Different Charge

[Robert Stanton]

Dear Tamas Karpati,

     Definitely, the question is basically what association energies are
for things which are bound ionically. It seems I require calculation of the
lone ions with compensating background charge, as well as the neutral
compound. I am just wondering how I can partially correct/change what these
absolute DFT energies are with respect to for valid comparison between
calculations. Is there a way to do this or do you think even if achieved,
this still might be a problematic approach? Thanks in advance!

Regards,
Robert Stanton

On Mon, Dec 28, 2020 at 12:20 PM Tamas Karpati <tkarpati at gmail.com> wrote:

> Dear Robert,
>
> Since each member of the series E(2-) ~ E(1-) ~ E ~ E(1+) ~ E(2+)
> etc... dwell on a different
> potential energy hypersurface, there is no direct physical meaning of
> their energy differences.
> Can you give the concrete question you try to answer?
>
> On the other hand, it can be quite useful to compare eg. the
> stabilization energies (or other
> derived energy-like quantities, even band positions). In case of the
> stab. ens. it is common to
> make hypothetical reactions and evaluate their energies which can then
> directly be compared.
>
> Hope this helps,
>   t
>
>
> On Mon, Dec 28, 2020 at 7:23 PM Robert Stanton <stantor at clarkson.edu>
> wrote:
> >
> > Dear all,
> >
> >     I am just wondering if there is, in general, an approach to
> comparing energies between two cells with different tot charge
> specifications? Is there a way for example to extrapolate the energy values
> to be w.r.t. vacuum to have a common comparison point?
> >
> >     I have seen somewhat similar questions, generally these are
> specifically for 2D system, where it's stated there are examples addressing
> this, but have not been able to find those examples in the QE install. Any
> information, or a pointer to this specific example (if it applies to more
> than just 2D) would be greatly appreciated! Thanks in advance for any help.
> >
> > Regards,
> > Robert Stanton
> > Graduate Student
> > Clarkson University
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