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qp2/docs/source/programs/fci.rst

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.. _fci:
.. program:: fci
===
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 :option:`determinants n_states`). The
|FCI| program will stop when reaching at least one the two following
conditions:
* number of Slater determinants > :option:`determinants n_det_max`
* abs(|PT2|) less than :option:`perturbation pt2_max`
The following other options can be of interest:
:option:`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).
:option:`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 |S^2| value corresponding to
:option:`determinants expected_s2`.
For excited states calculations, it is recommended to start with
:ref:`cis` or :ref:`cisd` guess wave functions, eventually in
a restricted set of |MOs|, and to set :option:`determinants s2_eig`
to |true|.
Needs:
.. hlist::
:columns: 3
* :c:data:`do_pt2`
* :c:data:`is_zmq_slave`
* :c:data:`mo_two_e_integrals_in_map`
* :c:data:`psi_coef`
* :c:data:`psi_det`
Calls:
.. hlist::
:columns: 3
* :c:func:`run_cipsi`
* :c:func:`run_slave_cipsi`
* :c:func:`run_stochastic_cipsi`
Touches:
.. hlist::
:columns: 3
* :c:data:`ci_electronic_energy`
* :c:data:`ci_electronic_energy`
* :c:data:`ci_energy`
* :c:data:`ci_electronic_energy`
* :c:data:`n_det`
* :c:data:`n_iter`
* :c:data:`psi_occ_pattern`
* :c:data:`c0_weight`
* :c:data:`distributed_davidson`
* :c:data:`psi_coef`
* :c:data:`psi_det_sorted_bit`
* :c:data:`psi_det`
* :c:data:`psi_det_size`
* :c:data:`psi_det_sorted_bit`
* :c:data:`psi_energy`
* :c:data:`psi_occ_pattern`
* :c:data:`psi_energy`
* :c:data:`pt2_e0_denominator`
* :c:data:`pt2_match_weight`
* :c:data:`pt2_overlap`
* :c:data:`pt2_stoch_istate`
* :c:data:`read_wf`
* :c:data:`selection_weight`
* :c:data:`state_average_weight`
* :c:data:`threshold_davidson_pt2`
* :c:data:`threshold_generators`
* :c:data:`variance_match_weight`