Charged Slab

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Charged Slab

Postby IBRAHIM » Wed Sep 26, 2018 6:24 am

Dear All,

I would like to ask about the calculation of charged slab using VASP. In manual, it is mentioned that "Total energies from charged slab calculations are hence useless....".

However, it seems that it is possible to use vasp for charged slabs as in this link viewtopic.php?f=4&t=17116

So is it possible that the total energy can be corrected for charged slabs?

Best regards,
Ibrahim
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Re: Charged Slab

Postby merzuk.kaltak » Wed Sep 26, 2018 12:56 pm

Dear Ibrahim

The link you are referring to says it is not possible to restrict additional charge to some region in the unit cell.
That is, you can change the total charge in the unit cell, but you cannot control where the additional charge goes.

The corresponding INCAR tag is NELECT, which sets the total number of electrons in a unit cell.
It is wise to inspect the charge density after changing NELECT from its default value to see where the additional charge goes.
In case you are satisfied with the effect of changin NELECT (no charge sloshing is present for instance) you should include dipole corrections in your calculation.

There's a caveat, though. For charged systems the dipole corrections are correct only for cubic supercells, see paragraph "charged cells" of this wiki entry.
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