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saeed_E

Member

Registered: 2019-12-21

Posts: 244

Are fragments need to be explicitly defined for DFT-SAPT?

Dear Tian,

As you know much better than me, a DFT-SAPT needs "grac_shift" values for monomers. Please consider the below template employed for a given DFT-SAPT calculation:

memory 55 gb

molecule {
0 1
F                  0.00000000    0.00000000   -1.85087700
H                  0.00000000    0.00000000   -0.86870700
--
-1 1
Cl                 0.00000000    0.00000000    1.03097600

units angstrom
no_reorient
symmetry c1
}

set {
    basis aug-cc-pVTZ
    df_basis_scf  aug-cc-pvtz-jkfit
    df_basis_sapt aug-cc-pvtz-ri
    scf_type DF
    guess sad
    freeze_core True
    sapt_dft_functional pbe0
    sapt_dft_grac_shift_a 0.157
    sapt_dft_grac_shift_b 0.215
}

energy('sapt(dft)')

The question is as follows:

the "sapt_dft_grac_shift_a" is always regarded to the monomer whose structure is given first (HF in the present case) and "sapt_dft_grac_shift_b" is always regarded to the monomer whose structure is given second (Cl anion in the present case). Is my statement quite correct?

If no, we should properly define monomer a (for which grac_shift_a is considered) and monomer b (for which grac_shift_b is considered). If possible, considering the given template, please let me know how these two monomers should explicitly and appropriately be defined in two blocks.

Sincerely,
Saeed

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Are fragments need to be explicitly defined for DFT-SAPT?

Correct.

saeed_E

Member

Registered: 2019-12-21

Posts: 244

Re: Are fragments need to be explicitly defined for DFT-SAPT?

Dear Tian,
Thank you very very much, my nice friend.

Sincerely,
Saeed