[CP2K-user] [CP2K:21128] Re: Counterpoise correction with Grimme D4

[Quentin Pessemesse]

Hi Holger, 
Counterpoise correction is a correction to the electronic energy, you 
should reason only on the electronic energies. The dispersion energy of the 
isolated fragments has no physical meaning, and the D3/D4 empirical 
correctoin plays no part in the BSSE as it is added after the SCF, and only 
depends on the geometry.
Here, I think CP2k is giving dispersion correction to the ghost atoms, 
calculating both the error that comes from basis functions of fragment 
being used to build the density of fragment B (BSSE), and adding some 
dispersion energy of the fragments and total system as well.
Instead of :
BSSE = (EA − EA(B)) + (EB − E (A)B)
You get:
([E(elec)A + E(disp)A] - [E(elec)A(B) - E(disp)AB]) + ([E(elec)B + 
E(disp)B] - [E(elec)(A)B - E(disp)AB]) = BSSE + (E(disp)A + E(disp)B - 
2*E(disp)AB)
Try to run the BSSE single point calculation without the empirical 
dispersion and substract it from the interaction energy you get with D3/D3 
correction. If it does not fix the issue, maybe I'm mistaken and something 
else is wrong.
Hope this helped :)
Q.
Le samedi 8 février 2025 à 13:36:41 UTC+1, Holger Sassnick a écrit :

> Hello,
>
> lately I have been trying to calculate the adsorption energy of water in 
> the CAU-23 MOF with different XC functionals. To avoid the quite 
> significant BSSE of CP2K's MOLOPT basis sets, I had to apply a counterpoise 
> correction.
>
> However, when using the Grimme D4 method the obtained values didn't really 
> make sense as they resulted in a positive interaction energy (I have 
> attached the corresponding input and output files). The  same calculation 
> with the PBE functional or PBE + Grimme D3 gives a negative interaction 
> energy (the absolute value is also significantly smaller).
>
> I was wondering whether this is a bug in the code? Would it be possible 
> that the ghost atoms are not properly treated by the interface to the DFTD4 
> library?
>
> I would be very grateful for some feedback.
>
> Thanks in advance and all the best,
> Holger 
>

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