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65 lines
1.8 KiB
ReStructuredText
65 lines
1.8 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
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function 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
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quantities related to it. One of these quantities are the natural
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orbitals which have the property of diagonalizing the one-body
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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
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defined 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|
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|MOs| as they are obtained from a correlated wave function. To use these
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orbitals for future calculations, one has to replace the current |MOs|
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by the natural orbitals. To do so, just run:
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.. code::
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qp_run save_natorb file.ezfio
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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
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calculations, the :ref:`save_natorb` program *automatically removes the
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current wave function* stored in the |EZFIO| database and replaces
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it by a single Slater determinant corresponding to a |HF| occupation
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of the new spin orbitals. Also, all the keywords to read the one-
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and two-electron integrals on the |MO| basis are set to ``None`` in
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order to be sure to avoid reading integrals incompatible with the
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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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