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60 lines
1.7 KiB
ReStructuredText
60 lines
1.7 KiB
ReStructuredText
===
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fci
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===
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|CIPSI| algorithm in the full configuration interaction space.
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The user point of view
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----------------------
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* :ref:`fci` performs |CIPSI| calculations using a stochastic scheme for both
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the selection and the |PT2| contribution,
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* :ref:`pt2` computes the |PT2| contribution using the wave function stored in
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the |EZFIO| database.
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The main keywords/options for this module are:
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* :option:`determinants n_det_max` : maximum number of Slater determinants in
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the |CIPSI| wave function. The :ref:`fci` program will stop when the size of
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the |CIPSI| wave function will exceed :option:`determinants n_det_max`.
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* :option:`perturbation pt2_max` : absolute value of the |PT2| to stop the
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|CIPSI| calculation. Once the abs(|PT2|) :math:`<` :option:`perturbation pt2_max`,
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the |CIPSI| calculation stops.
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* :option:`determinants n_states` : number of states to consider in the |CIPSI|
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calculation.
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* :option:`determinants read_wf` : if |false|, starts with a |ROHF|-like
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determinant, if |true|, starts with the current wave function(s) stored in
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the |EZFIO| directory.
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.. note::
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For a multi-state calculation, it is recommended to start with :ref:`cis`
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or :ref:`cisd` wave functions as a guess.
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* :option:`determinants expected_s2` : expected value of |S^2| for the
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desired spin multiplicity.
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* :option:`determinants s2_eig` : if |true|, systematically add all the
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determinants needed to have a pure value of |S^2|. Also, if |true|, it
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tracks only the states having the good :option:`determinants expected_s2`.
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The programmer's point of view
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------------------------------
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This module was created with the :ref:`module_cipsi` module.
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.. seealso::
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The documentation of the :ref:`module_cipsi` module.
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