Atomic numbers limit in SAPT?

SAPT
1

Dear all,
Recently, I want to use the Psi4 program to perform SAPT calculation. The total atomic number in my system is about 160. Monomer 1 has 110 atoms, and monomer 2 has 50 atoms. I have done some SAPT testing task, e.g., pentacene dimer, and can calculate successfully. I want to know that can I use the SAPT for my real system.

Thanks a lot,
Best regards,

2

No hard limit, no.
Computer memory and disk space requirement are modest for SAPT0/jun-cc-pVDZ, but even this will eventually reach the limits of your computer at some point.

3

Dear hokru,
Thanks for your quily reply.

molecule three_DIMER{
0 1
XXX # atomic symbol and coordinates

0 1
XXX
unit angstrom
}

set globals{
basis jun-cc-pvtz
guess sad
scf_type df

}

set sapt{
print 1
nat_orbs_t2 true
freeze_core true
}
memory 48 Gb
psi4.set_num_threads(12)
energy(‘sapt0’)

Unfortunately, I got the error:

==> Pre-Iterations <==

Irrep   Nso     Nmo     Nalpha   Nbeta   Ndocc  Nsocc

 A       4412    4412       0       0       0       0

Total    4412    4412     303     303     303       0

Traceback (most recent call last):
File “/home/taipinghu/opt/psi4conda/bin/psi4”, line 248, in
exec(content)
File “”, line 194, in
File “/home/taipinghu/opt/psi4conda/lib//python2.7/site-packages/psi4/driver/driver.py”, line 460, in energy
wfn = procedures[‘energy’][lowername](lowername, molecule=molecule, **kwargs)
File “/home/taipinghu/opt/psi4conda/lib//python2.7/site-packages/psi4/driver/procrouting/proc.py”, line 3184, in run_sapt
dimer_wfn = scf_helper(‘RHF’, molecule=sapt_dimer, **kwargs)
File “/home/taipinghu/opt/psi4conda/lib//python2.7/site-packages/psi4/driver/procrouting/proc.py”, line 1330, in scf_helper
e_scf = scf_wfn.compute_energy()

RuntimeError:
Fatal Error: PSIO Error
Error occurred in file: /scratch/psilocaluser/conda-builds/psi4_1495009270718/work/psi4/src/psi4/libpsio/error.cc on line: 129
The most recent 5 function calls were:

psi::PsiException::PsiException(std::__cxx11::basic_string<char, std::char_traits, std::allocator >, char const*, int)
psi::psio_error(unsigned int, unsigned int)
psi::PSIO::rw(unsigned int, char*, psi::psio_address, unsigned long, int)
psi::PSIO::write_entry(unsigned int, char const*, char*, unsigned long)
psi::Matrix::save(psi::PSIO*, unsigned int, psi::Matrix::SaveType)

I can calculate successfully SAPT for small testing molecules using this keyword.

Thanks a lot,
regards

4

SAPT0 usually works best with the jun-cc-pVDZ basis as it relies on error compensation to some extend. A larger basis wont necessarily provide better results.

Did you set a large enough local disk as scratch directory?

5

Dear hokru,
According to your suggestion, I have set the scratch directory using the command “export PSI_SCRATCH=/XXX”. Now it is calculating normally and No errors at the moment.
Ok, I will use the jun-cc-pVDZ basis set. Another question is that if my keyword is correct or suitable for my purpose？

Thanks a lot.

6

Looks sensible for most applications. Some are anyway already default.

7

Thanks a lot again.
Thanks for your quick reply.
I will report my results for you later.

regards.

8

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