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I am trying to understand the function of dipole correction in DFT. I find that there are two examples related to this topic on the VASP wiki.
The first case is about CO on Ni 111 surface
The input INCAR file is :

 general:
   ENMAX = 400
   SYSTEM = CO adsorption on Ni(111)
   ISMEAR = -5
   ALGO= Fast

 LDOS:
   LORBIT = 11

 workfunction:
   IDIPOL=3
   LDIPOL= .TRUE.
   LVHAR = .TRUE.
#  LVTOT = .TRUE.

enter image description here

The second case is about Adsorption of H2O on TiO2
The input INCAR file is :

SYSTEM   = H2O_TiO2
ENMAX    = 400
ISMEAR   =  2
SIGMA = 0.05
EDIFF = 1e-6
EDIFFG = -0.05
IBRION = 2
POTIM = 0.5
NSW = 200

enter image description here

Apparently, the slabs of these two cases are both asymmetric, but it seems that the second case doesn't set dipole correction.
As far as I understand, when the slab model is asymmetric, I should always use dipole correction. My question is:
When should I use dipole correction?

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1 Answer 1

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With a large enough vacuum, you don't need a dipole correction as badly to get good results. Sometimes the correction can cause convergence issues or problems with single steps giving incorrect energies.

The second calculation looks like a geometry optimization, so maybe this was done to improve stability; a dipole correction should be applied after converging the structure, but its not critical beforehand.

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