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QuantumPackage/man/natural_orbitals.1

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.TH "NATURAL_ORBITALS" "1" "Jan 17, 2019" "2.0" "Quantum Package"
.SH NAME
natural_orbitals \- | Quantum Package >
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.SH SUMMARY
.sp
To produce state\-average natural orbitals, run
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.nf
.ft C
qp_run save_natorb file.ezfio
.ft P
.fi
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.sp
The MOs will be replaced, so the two\-electron integrals and the wave function
are invalidated as well.
.SH EXTRACTING NATURAL ORBITALS
.sp
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:
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.ce
\erho_{ij} = \edelta_{ij}
.ce 0
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where the element of the one\-body density matrix \erho_{ij} is define as:
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.ce
\erho_{ij} = \elangle \ePsi | \eleft( a^{\edagger}_{j,\ealpha} a_{i,\ealpha} + a^{\edagger}_{j,\ebeta} a_{i,\ebeta} \eright) |\ \ePsi\ \erangle
.ce 0
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.sp
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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.sp
.nf
.ft C
qp_run save_natorb file.ezfio
.ft P
.fi
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.SH HANDS ON
.sp
\fBIMPORTANT:\fP
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As the MOs are changed, for the sake of coherence of future calculations, the save_natorb program
\fIautomatically removes the current wave function\fP stored in the \fI\%EZFIO\fP 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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.sp
\fBSEE ALSO:\fP
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The documentation of the \fBsave_natorb()\fP program.
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.SH AUTHOR
A. Scemama, E. Giner
.SH COPYRIGHT
2018, A. Scemama, E. Giner
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