[Pw_forum] How to calculate charged system binding energy?

[Bahadır salmankurt]

Dear Mostafa Y.

thanks for the useful informations

2015-07-19 5:29 GMT+03:00 Mostafa Youssef <myoussef at mit.edu>:

>  Dear Bahadir
>
> First, charged slabs are problematic because their total energy does not
> converge with respect to vacuum thickness. You can test on a simple model.
> However, there is a trick to go around this by inserting a dopant far a way
> from the critical reaction zone.  For example suppose you want to study +1
> charged defect on ZrO2 surface.  Then you can insert one Y ion(typically 3+
> and hence -1 with respect to Zr4+) .   This should generate a positive
> charge somewhere else in the slab and one hopes that this positive charge
> will localize correctly where you expect it to localize.  But one has to be
> cautious because this also generates a large dipole across the slab. One
> way to go around this by symmetrizing the slab such that dipoles cancel.
>
>
> Second, even if charged slabs work, I think you are not conserving the
> charge when you calculate the binding energy. Because you mentioned you
> used  tot_charge=-1 in the slab+molecule , slab only, molecule only. To me
> this will not conserve the charge when you calculate the binding energy
> (B.E.)
>
> B.E. =(slab+molec.)  - (slab) - (molec)
>
> Although I have seen papers defining binding energies that do not conserve
> the charge, I do not think this is meaningful.
>
> Mostafa Y.
> MIT
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20150720/9747e7ff/attachment.html>