[QE-users] Adsorption energy between charged slab + anion

[Stefano Baroni]

If the anion stays charged, which is an issue by itself in DFT, the distance will never be large enough, because the slab will generate a macroscopic electric field. sb

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Stefano Baroni, Trieste -- http://stefano.baroni.me

> On 23 Feb 2021, at 07:05, Nam Tran <vnt981 at uowmail.edu.au> wrote:
> 
> 
> Dear QE users,
> 
> I would like to calculate the adsorption energy of a negative anion NO3- with a positive slab (The total system is neutral). I cannot use the convention formula Eds = E(slab+anion) - E(slab) - E(anion) because of the charge compensation when calculating the energy of charged slab and charge adsorbate. 
> 
> As the total system (slab+anion) is neutral, I wonder if it is possible to just move the molecule far away from the slab (make sure that vacuum in z-direction is large enough), and calculate the energy difference i.e., one of them the molecule is far away from the surface and in the other one the molecule adsorbed on the surface.
> 
> 
> Best regards
> Nam
> 
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