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" }
]