Your kind attention is highly appreciated, my nice friend.

I well studied that part of Multiwfn manual you nicely introduced me and, to some extent, I understood the positive origin of E_Pauli.
It seems, in addition to GAMESS-US, ADF is also able to perform interaction energy decomposition and giving us the value of Delta_E(Pauli) as mentioned in the above-mentioned formula unless you mean a specific usage of GAMESS which I am not aware of that.

Sincerely,
Saeed

I have mentioned this point in the section of introducing ETS-NOCV theory, see Section 3.26.1 of Multiwfn manual.

You can use GAMESS-US to perform energy decomposition analysis, this term can be found from the result.

Best regards,

Tian

Within the Zigler-Morokama approach, interaction energy is decomposed into:

Delta_E= Delta_V(elst)+Delta_E(Pauli)+delta_E(orbital)+delta_E(dis)

Delta_V(elst) represents the electrostatic interaction between oppositely charged regions (electrons and nuclei) of two monomers and is evidently understandable.

On the other hand, Delta_E(Pauli) is a repulsive component between occupied orbitals of two fragments. It is quite clear that Delta_E(Pauli) is responsible for a happening much more important than a simple repulsion between same charged particles (electrons). If Delta_E(Pauli) just represents a repulsion between electrons, it could simply be included into Delta_V(elst) as a sub-part. Consequently, it becomes evident that Delta_E(Pauli) mainly originates from a concept namely "exchange". Is it quite correct? If so, please let me know why this component (Pauli exchange) is repulsive in nature? Indeed, what happening(s) make this component to be positive portraying a destructive effect on the interaction energy? Also, please let me know how we can simply compute value of Pauli-exchange energy for an isolated species using routine codes such as Gaussian or Orca.

Sincerely,
Saeed