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Arivu

Member

Registered: 2025-12-27

Posts: 13

STEOM-DLPNO-CCSD for S1-T1 energy gap calculations input

Dear All,
    I am trying to calculate the S1-T1 energy gap using STEOM-DLPNO-CCSD method. Here is my input below. But the calculation fails every time, saying EOM convergence failed. Is there a problem with my input? Kindly help me out.

"
! STEOM-DLPNO-CCSD def2-SVP def2-SVP/C def2/J TightSCF
! PrintBasis MiniPrint PrintMOs
! xyzfile

%pal nprocs 48 end
%maxcore 12000

%mdci
NRoots 1
DoTriplet true
DoRootWise true
OThresh 0.005
VThresh 0.005
TCutPNOSingles 1e-11
NDAV 400
DoStoreSTEOM true
DoSimpleDens false
AddL2Term True
DTol 1e-5
end

* xyzfile
"

Some papers mention a single-point calculation on the S1 and T1 optimized geometry to calculate the energy gap. If it is so, what will be the input for calculating a single-point using STEOM-DLPNO-CCSD method?

Thanks and Regards
Arivu

sobereva

Tian Lu (Multiwfn developer)

From: Athens, Greece

Registered: 2017-09-11

Posts: 2,286

Website

Re: STEOM-DLPNO-CCSD for S1-T1 energy gap calculations input

STEOM-CCSD is not a blackbox method, in ORCA manual there are some discussions about fine-tune for the calculation, which affects convergence. If it doesn't work after various attempts, try to consider other methods with similar accuracy, such as the efficient LR-CC2 in e^T code (greatly accelerated by Cholesky decomposition).

"a single-point using STEOM-DLPNO-CCSD method" means calculating excited state energy (namely sum of excitation energy and ground state energy) at the given structure.

Best regards,

Tian Lu

Arivu

Member

Registered: 2025-12-27

Posts: 13

Re: STEOM-DLPNO-CCSD for S1-T1 energy gap calculations input

Dear Prof. Tian,
     Thank you so much for your answer and new suggestions for e^T code. I shall try them.
Regards
Arivu