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saeed_E

Member

Registered: 2019-12-21

Posts: 237

Fitting exponents for SCF and Correlation energies

Dear Tian,
I am working on different series of complexes for which the CBS extrapolation using Psi4 is the main goal.
You know much better than me such an extrapolation needs two numerical values as input namely "scf_alpha" and "corl_alpha". Please let me ask have we to enter these values in the input file or we can allow Psi4 uses the default values?
Moreover, if possible, please let me know where I can find a complete list of the recommended values of these quantities for below extrapolation (the Orca 5 manual does not provide a complete list of these values):

cc-pVDZ---->cc-pVTZ;
aug-cc-pVDZ---->aug-cc-pVTZ;
cc-pVTZ---->cc-pVQZ;
aug-cc-pVTZ---->aug-cc-pVQZ;
def2-DZVPP---->def2-TZVPP;
def2-TZVPP---->def2-QZVPP

Yours sincerely,
Saeed

Last edited by saeed_E (2024-08-16 04:01:52)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,760

Website

Re: Fitting exponents for SCF and Correlation energies

I don't have any experience in using PSI4 to perform basis set extrapolation.

saeed_E

Member

Registered: 2019-12-21

Posts: 237

Re: Fitting exponents for SCF and Correlation energies

Dear Tian,
Too many thanks for your kind attention.
When we employ Orca to perform extrapolation, the value of "SCF_alpha" and "Corl_alpha" used by the code during extrapolation is printed out at the end of output file. These values are quite dependent on the basis sets we consider for extrapolation. For instance, using aug-cc-pVTZ--->aug-cc-pVQZ, "SCF_alpha"=5.79 and "Corl_alpha"=3.05.

The question is that:
are we allowed to use these values for the same extrapolation using PSi4?

Sincerely,
Saeed

saeed_E

Member

Registered: 2019-12-21

Posts: 237

Re: Fitting exponents for SCF and Correlation energies

Dear Tian,
Through some simple tests I found that if "SCF_alpha" and "Corl_alpha" values used by Orca are employed within a SAME extrapolation in PSI4, we reach a quite same and identical result. That is, PSI4 also exactly uses the approaches employed by Orca through extrapolations.

Sincerely,
Saeed