EOM-CCSD job FOR SINGLET TRIPLET STATE in Q-Chem stuck during SCF convergence

Questions
#1

I am trying to run an excited-state calculation in Q-Chem 6.3 using EOM-CCSD with the def2-TZVP basis set. My input is:
$rem
METHOD eom-ccsd
BASIS def2-TZVP
JOBTYPE SP
GUI 2
CC_TRANS_PROP 1
EE_TRIPLETS 3
EE_SINGLETS 3
AUX_BASIS RIJK-def2-TZVP
MEM_TOTAL 300000
CC_MEMORY 290000
CC_BACKEND XM
FROZEN_CORE TRUE
USE_LIBPT TRUE
CC_SINGLE_PREC 2
EOM_SINGLE_PREC 1
CC_SP_T_CONV 4
CC_SP_E_CONV 6
CC_ERASE_DP_INTEGRALS 1
LIBPT_MIXED_PRECISION 1
STATE_ANALYSIS TRUE
CC_EOM_PROP TRUE
CC_EOM_PROP_TE TRUE
CC_REF_PROP 1
NTO_PAIRS 2
SYM_IGNORE TRUE
CC_SYMMETRY FALSE
$end
The job never passes the SCF step — it just hangs without converging. I have tried tightening and loosening convergence thresholds, but no progress.

  1. Are there known issues with SCF convergence for EOM-CCSD with wb97x-d3 orbitals or with large memory allocation?
  2. Should I switch to a different reference (e.g. RHF → MP2 → CCSD)?
  3. Are there recommended keywords for improving SCF stability before the EOM-CCSD part starts (e.g. SCF_ALGORITHM, SCF_CONVERGENCE, GUESS_CORE, DIIS_GUESS)?
    Any advice even for pbs file ?
    Any advice on how to get the SCF to converge in this setup would be greatly appreciated.
#2

My comments are basically same as

Probably you simply need to tighten THRESH if you’re seeing convergence problems (and if so there’s probably a warning in the output that you’re ignoring). This may simply be too large - how many basis functions is it?