Psimrcc energy calculation not right for symmetry c1

[ABQTrap]

Dear all,
I tried to run the Mk-MRCCSD sample input file (Water molecule with symmetry) provided by PSI4 documentaion, and it ran successfully. The input file is shown below:

molecule o2 {
   0 3
   O
   O 1 2.265122720724
   units au
}
set {
   basis cc-pvtz
}
set mcscf {
   reference       rohf
   docc            [3,0,0,0,0,2,1,1]      # Doubly occupied MOs
   socc            [0,0,1,1,0,0,0,0]      # Singly occupied MOs
}
set psimrcc {
   corr_wfn        ccsd                   # Do Mk-MRCCSD
   frozen_docc     [1,0,0,0,0,1,0,0]      # Frozen MOs
   restricted_docc [2,0,0,0,0,1,1,1]      # Doubly occupied MOs
   active          [0,0,1,1,0,0,0,0]      # Active MOs
   frozen_uocc     [0,0,0,0,0,0,0,0]      # Frozen virtual MOs
   corr_multp      1                      # Select the Ms = 0 component
   follow_root     1
   wfn_sym         B1g                    # Select the B1g state
}
energy('psimrcc')

The output file could be found here.
h2o-mkmrccsd.dat (21.9 KB)

However, if I use the symmetry C1 while keeping other parameters all the same, then the calculation energy became weird, and could not converge.
The input file is shown below:

memory 40GB

molecule o2 {
   0 3
   O
   O 1 2.265122720724
   units au
   symmetry c1
}
set {
   basis cc-pvdz
}
set mcscf {
   reference       rohf
   docc            [7]      # Doubly occupied MOs
   socc            [2]      # Singly occupied MOs
}
set psimrcc {
   corr_wfn        ccsd                   # Do Mk-MRCCSD
   frozen_docc     [2]      # Frozen MOs
   restricted_docc [5]      # Doubly occupied MOs
   active          [2]      # Active MOs
   frozen_uocc     [0]      # Frozen virtual MOs
   corr_multp      1                      # Select the Ms = 0 component
   follow_root     1
#  wfn_sym         B1g                    # Select the B1g state
}
energy('psimrcc')

The output file of symmetry C1 coud be found here.
h2o-mkmrccsd-c1.dat (19.8 KB)

I am new to PSI4, so if I make any mistake with the input file, please let me know. Thanks in advance.

[OliP]

I think it’s a convergence problem.
Please try
tikhonow_max 40
tikhonow_omega 0.005
But use the same basis set (cc-pvtz) in order to see energy differences

[ABQTrap]

Dear Olip,

Thank you so much for your reply. After adding these two parameters, the input file ran smoothly, and if I use the same basis set, the energies are almost identical when symmetry is applied or not.
Thanks again.