fci

Selected Full Configuration Interaction with stochastic selection and PT2.

This program performs a CIPSI-like selected CI using a stochastic scheme for both the selection of the important Slater determinants and the computation of the PT2 correction. This CIPSI-like algorithm will be performed for the lowest states of the variational space (see determinants n_states). The FCI program will stop when reaching at least one the two following conditions:

• number of Slater determinants > determinants n_det_max
• PT2 < perturbation pt2_max

The following other options can be of interest:

determinants read_wf

When set to false, the program starts with a ROHF-like Slater determinant as a guess wave function. When set to true, the program starts with the wave function(s) stored in the EZFIO directory as guess wave function(s).

determinants s2_eig

When set to true, the selection will systematically add all the necessary Slater determinants in order to have a pure spin wave function with an \(\widehat{S^2}\) value corresponding to determinants expected_s2.

For excited states calculations, it is recommended to start with .cis. or .cisd. guess wave functions, eventually in a restricted set of MOs, and to set determinants s2_eig to true.

Needs:

psi_coef is_zmq_slave

do_pt2 mo_two_e_integrals_in_map

psi_det

Calls:

run_cipsi()

run_slave_cipsi()

run_stochastic_cipsi()

Touches:

ci_electronic_energy ci_electronic_energy ci_energy ci_electronic_energy n_det psi_occ_pattern c0_weight

distributed_davidson psi_coef psi_det_sorted_bit psi_det psi_det_size psi_det_sorted_bit

psi_occ_pattern pt2_e0_denominator pt2_stoch_istate read_wf state_average_weight threshold_generators