Multiwfn forum

saeed_E

Member

Registered: 2019-12-21

Posts: 244

Difference between Orbitals interaction from sobEDAW and ETS-NOCV

Dear Tian,

I performed a sobEDAW analysis on a given complex. The value of delta_E_orb was obtained to be -47.67 kcal/mol. Alternatively, I also performed an ETS-NOCV analysis on the considered complex to find how delta_E_orb (obtained from sobEDAW) is distributed between different ETS-NOCV pairs. The value of "Sum of pair energies", -82.16 kcal/mol, significantly differs from the value of delta_E_orb, -47.67 kcal/mol, while both analyses were performed at a quite identical level, i.e. B3LYP-GD3(BJ)/6-311+G(2d,p). If possible, please let me ask is it generally true to expect the value of delta_E_orb from sobEDAW analysis to be identical with the value of "Sum of pair energies" from ETS-NOCV (personally, I think no due to significant difference between SobEDAW and ETS-NOCV algorithms) ? If so, could you please let me know why these two values display such a considerable difference?

Yours sincerely,
Saeed

Last edited by saeed_E (2023-12-30 18:24:05)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Difference between Orbitals interaction from sobEDAW and ETS-NOCV

Dear Saeed,

I suggest removing diffuse function and check the difference again.

Difference is expected, but usually not large.

Tian

saeed_E

Member

Registered: 2019-12-21

Posts: 244

Re: Difference between Orbitals interaction from sobEDAW and ETS-NOCV

Dear Tian,
Too many thanks for your kind attention, my nice friend. As you so nicely recommended, removing diffuse functions led to very satisfying results. Indeed, employing 6-311G(2d,p) basis set, there is a very small difference by 0.86 kcal/mol. Meanwhile, in my current systems studied, there are some cases in which this difference reaches about 10 kcal/mol. Is such a difference sound scientific (logical) and accepted?

Your valuable time and professional recommendations are highly appreciated.

Sincerely,
Saeed

Last edited by saeed_E (2023-12-31 10:47:53)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Difference between Orbitals interaction from sobEDAW and ETS-NOCV

Dear Saeed,

So, I suggest using a basis set without diffuse functions, since diffuse funcions often lead to numerical instability and causes unexpected problems.

Sum of all orbital interactions given by current implementation of ETS-NOCV in Multiwfn is not exactly identical to delta_E_orb, this point has been described in Multiwfn manual, please see the paragraph beginning with "The energies of NOCV orbitals in Multiwfn are not calculated in the strict way of the standard ETS-NOCV method as described above!" in Section 3.26.2 of Multiwfn manual. Even though there is a certain discrepancy, it doesn't hinder discussing the nature of orbital interaction.

Best,

Tian

saeed_E

Member

Registered: 2019-12-21

Posts: 244

Re: Difference between Orbitals interaction from sobEDAW and ETS-NOCV

Dear Tian,
Your very informative and perfect comments are deeply appreciated, my nice friend. As always, I highly enjoyed and learned.

Sincerely yours,
Saeed