# 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" }
]
```