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55 lines
1.7 KiB
ReStructuredText
55 lines
1.7 KiB
ReStructuredText
Natural orbitals
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================
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Summary
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-------
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To produce state-average natural orbitals, run ::
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qp_run save_natorb file.ezfio
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The MOs will be replaced, so the two-electron integrals and the wave function
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are invalidated as well.
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Extracting natural orbitals
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---------------------------
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Once obtained the near |FCI| wave function, one can obtain many quantities related to it.
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One of these quantities are the natural orbitals which have the properties of diagonalizing the one-body density matrix:
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.. math::
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\rho_{ij} = \delta_{ij}
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where the element of the one-body density matrix :math:`\rho_{ij}` is define as:
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.. math::
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\rho_{ij} = \langle \Psi | \left( a^{\dagger}_{j,\alpha} a_{i,\alpha} + a^{\dagger}_{j,\beta} a_{i,\beta} \right) | \Psi \rangle
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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:
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.. code::
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qp_run save_natorb hcn
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Hands on
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--------
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.. important::
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As the |MOs| are changed, for the sake of coherence of future calculations, the save_natorb program
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*automatically removes the current wave function* stored in the |EZFIO| database and replace
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it by a single Slater determinant corresponding to a |HF| occupation of the new spin orbitals.
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Also, all the keywords to read the one- and two-electron integrals on the |MO| basis are set to "None"
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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 :ref:`save_natorb` program.
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