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Natural orbitals
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Summary
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To produce state-average natural orbitals, run ::
qp_run save_natorb file.ezfio
The MOs will be replaced, so the two-electron integrals and the wave function
are invalidated as well.
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Extracting natural orbitals
---------------------------
Once obtained the near |FCI| wave function, one can obtain many quantities related to it.
One of these quantities are the natural orbitals which have the properties of diagonalizing the one-body density matrix:
.. math ::
\rho_{ij} = \delta_{ij}
where the element of the one-body density matrix :math: `\rho_{ij}` is define as:
.. math ::
\rho_{ij} = \langle \Psi | \left( a^{\dagger}_{j,\alpha} a_{i,\alpha} + a^{\dagger}_{j,\beta} a_{i,\beta} \right) | \Psi \rangle
These orbitals are in general known to be better than the usual |HF| |MOs| as they are obtained from a correlated wave function. To use these orbitals for future calculations, one has to replace the current |MOs| by the natural orbitals. To do so, just run:
.. code ::
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qp_run save_natorb file.ezfio
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Hands on
--------
.. important ::
As the |MOs| are changed, for the sake of coherence of future calculations, the save_natorb program
*automatically removes the current wave function* stored in the |EZFIO| database and replace
it by a single Slater determinant corresponding to a |HF| occupation of the new spin orbitals.
Also, all the keywords to read the one- and two-electron integrals on the |MO| basis are set to "None"
in order to be sure not to read integrals not corresponding to the current set of |MOs|.
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.. seealso ::
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The documentation of the :c:func: `save_natorb` program.
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