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46 lines
1.3 KiB
ReStructuredText
46 lines
1.3 KiB
ReStructuredText
===
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cis
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===
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This module contains a |CIS| program.
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The user point of view
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----------------------
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The :ref:`cis` program performs the CI to obtain the ROHF reference + all
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single excitations on top of it. This program can be very useful to:
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* **Ground state calculations**: generate a guess for the ground state wave
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function if one is not sure that the :ref:`scf` program gave the lowest |SCF|
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solution. In combination with :ref:`save_natorb` it can produce new |MOs| in
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order to reperform an :ref:`scf` optimization.
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* **Excited states calculations**: generate guesses for all the
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:option:`determinants n_states` wave functions, that will be used by the
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:ref:`fci` program.
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The main keywords/options to be used are:
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* :option:`determinants n_states`: number of states to consider for the |CIS| calculation
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* :option:`determinants s2_eig`: force all states to have the desired value of |S^2|
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* :option:`determinants expected_s2`: desired value of |S^2|
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The programmer's point of view
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------------------------------
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This module was built by setting the following rules:
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* The only generator determinant is the Hartree-Fock (single-reference method)
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* All generated singly excited determinants are included in the wave function (no perturbative
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selection)
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These rules are set in the ``H_apply.irp.f`` file.
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