[Pw_forum] Lowdin Charge - sign

[David Grifith]

Dear Stefano de Gironcoli

Thanks a lot for your instructive and informative comments.

-- 
Sincerely Yours
David G.
JCU


> In a pseudopotential calculation core electrons are not there so if you
> want to "see" the core electrons you need to do an all-electron
> calculation or a PAW calculation where the total charge is reconstructed.
> If you are interested in knowing a total atomic charge this is easy...
> just add to the valence electron charge the number of (completely
> filled) core electrons, change sign and add the nuclear charge..
> notice however that the decomposition of a charge distribution in
> atomic contribution is a somewhat ill defined procedure and Lowdin
> procedure is just one possibility, so do not attach too much
> significance to minor changes from system to system...
>
> Something that can be useful to identify bonding in your system can be
> the analysis of the projected density of states on atomic levels of
> nearest-neighbor atoms. It is sometime possible to see peaks occurring
> in the same energy range for the two atoms that signal that electronic
> states in that energy range are shared between the two atoms as one
> expect in a covalent bond.
>
> Hope it helps.
>
> Stefano de Gironcoli
>

David Grifith wrote:
>* Dear Heather
*>*
*>* Thanks for your comments. I think that this type of charge (Lowdin) which is
*>* nearly the number of valence electrons can not speak about the details of
*>* the system.
*>* Some electrons are bonding and also, the effect of the core (core electron +
*>* nucleus ) is not negligible. I want to compare the real charge of two atoms
*>* in my system with each other not their valence electrons. I appreciate your
*>* help in advance.
*
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