#! Mk-MRCCSD(T) single point. $^1A@@1$ CH2 state described using
#! the Ms = 0 component of the singlet.  Uses RHF singlet orbitals.

memory 550 mb


molecule ch2 {
  0 1
  C         0.000000000000    -0.071831139101     0.000000000000
  H         2.056713670133     0.427640533717     0.000000000000
  H        -2.056713670133     0.427640533717     0.000000000000

  units au
}

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

set mcscf {
  reference       rhf
  # The socc and docc needn't be specified; in this case the code will converge correctly without
  docc            [2,0,1,1]      # Doubly occupied MOs
  socc            [0,0,0,0]      # Singly occupied MOs
}

set psimrcc {
  corr_wfn        ccsd_t         # Do Mk-MRCCSD(T)
  frozen_docc     [0,0,0,0]      # Frozen MOs
  restricted_docc [2,0,1,1]      # Doubly occupied MOs
  active          [0,0,0,0]      # Active MOs
  frozen_uocc     [0,0,0,0]      # Frozen virtual MOs
  corr_multp      1              # Select the Ms = 0 component
  wfn_sym         A1             # Select the A1 state
}

energy('psimrcc')