#! Mk-MRCCSD single point. $^3 \Sigma ^-$ O2 state described using
#! the Ms = 0 component of the triplet.  Uses ROHF triplet orbitals.


molecule o2 {
  0 3
  O
  O 1 2.265122720724

  units au
}

set {
  basis cc-pvtz
  e_convergence 10
  d_convergence 10
  r_convergence 10
}

set mcscf {
  reference       rohf
  # The socc and docc needn't be specified; in this case the code will converge correctly without
  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
  wfn_sym         B1g                    # Select the B1g state
}

energy('psimrcc')
