Post HF methods#

In this section, we specify the PySCF calculation to be compared with the simulator. You can calculate energy and other physical quantities. See Output chemical properties section for details. If num_excited_states is set to a value larger than 0, CASCI, CASSCF and CISD calculate the electronic excitations as well.

You can choose one of the following methods.

  • MP2

  • CISD

  • CCSD

  • CASCI

  • CASSCF

  • FCI

For CASSCF, you can select the method for calculating electronically excited states from the following

  • STATE_AVERAGED: the default, where each electronic excited state is equally weighted. STATE_AVERAGED: default, equal weight for each electronic excited state.

  • STATE_SPECIFIC.

Notes#

  • CISD does not support the density fitting approximation.

  • Except for CCSD, if the density-fitting approximation is enabled, first-order differentiation in nuclear coordinates is not possible.

  • For systems with a periodic boundary condition, MP2, CCSD, and CASCI (ground energy only) are supported.

Input example#

"post_hf_methods": [
  { "type": "MP2" },
  { "type": "CISD" },
  { "type": "CCSD" },
  {
    "type": "CASCI",
    "excited_state_type": "STATE_AVERAGED"
  },
  {
    "type": "CASSCF",
    "excited_state_type": "STATE_SPECIFIC"
  },
  { "type": "FCI" }
]