BSSE calculation

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BSSE calculation

Date: 2024/06/20 03:58
Name: Amina <aminacharef60@gmail.com>: Dear professors,

I have a question about the BSSE energy calculation using the counterpoise method with OpenMX software:

When we calculate the energy of fragment A with ghost atoms of B (denoted as "E(A)B"), should we first optimize this system while applying the DFT-D method? And then, should we calculate a single point energy for this system while keeping the DFT-D method applied?

Because when considering the entire system AB, we first optimized the structure of AB with the DFT-D method, and then calculate a single point energy with the DFT-D method turned on.

I have the same question for fragment B with ghost atoms of A (denoted as "E(B)A").

Thank you very much for your help.
Best regards.
Amina.

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Re: BSSE calculation ( No.1 )

Date: 2024/07/11 23:25
Name: T. Ozaki

Hi,

Once you decide to employ the DFT-D method, all the calculations should be
consistently performed with the DFT-D method to main the approximation.

Step 1:
The counterpoise correction energies can be estimated with the optimized structure
of the entire system AB. The one-shot total energy calculations are performed
for the real A + ghost B system and the ghost A + real B system to estimate
the correction energies.

Step 2:
If you want to include the relaxation effect of the isolated A and isolated B systems,
you can perform the geometry optimizations for both the systems independently without
introducing the ghost atoms. The counterpoise correction energies borrowed from the
calculations of the step 1 are added to the sum of total energies for the isolated systems.

Regards,

TO

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