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132 lines
3.0 KiB
Groff
132 lines
3.0 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "CIS" "1" "Jan 25, 2019" "2.0" "Quantum Package"
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.SH NAME
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cis \- | Quantum Package >
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.
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.nr rst2man-indent-level 0
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..
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.de1 INDENT
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.\" .rstReportMargin pre:
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.\" .rstReportMargin post:
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.de UNINDENT
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. RE
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.\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
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.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
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..
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.INDENT 0.0
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.INDENT 3.5
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Configuration Interaction with Single excitations.
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.sp
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This program takes a reference Slater determinant of ROHF\-like
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occupancy, and performs all single excitations on top of it.
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Disregarding spatial symmetry, it computes the \fIn_states\fP lowest
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eigenstates of that CI matrix. (see \fBdeterminants n_states\fP)
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.sp
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This program can be useful in many cases:
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.sp
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To be sure to have the lowest SCF solution, perform an scf
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(see the hartree_fock module), then a \fI\%cis\fP, save
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the natural orbitals (see save_natorb) and re\-run an
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scf optimization from this MO guess.
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.sp
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The lowest excited states are much likely to be dominated by
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single\-excitations. Therefore, running a \fI\%cis\fP will save
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the \fIn_states\fP lowest states within the CIS space in the \fI\%EZFIO\fP
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directory, which can afterwards be used as guess wave functions for
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a further multi\-state FCI calculation if \fBdeterminants read_wf\fP
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is set to \fBtrue\fP before running the fci
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executable.
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.sp
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If \fBdeterminants s2_eig\fP is set to \fBtrue\fP, the CIS
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will only retain states having the expected \ewidehat{S^2} value (see
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\fBdeterminants expected_s2\fP). Otherwise, the CIS will take
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the lowest \fBdeterminants n_states\fP, whatever multiplicity
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they are.
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.sp
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\fBNOTE:\fP
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.INDENT 0.0
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.INDENT 3.5
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To discard some orbitals, use the qp_set_mo_class
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command to specify:
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.INDENT 0.0
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.IP \(bu 2
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\fIcore\fP orbitals which will be always doubly occupied
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.IP \(bu 2
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\fIact\fP orbitals where an electron can be either excited from or to
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.IP \(bu 2
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\fIdel\fP orbitals which will be never occupied
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.sp
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Needs:
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.INDENT 0.0
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.INDENT 2.0
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.IP \(bu 2
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\fBread_wf\fP
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.UNINDENT
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.INDENT 2.0
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.UNINDENT
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.INDENT 2.0
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.UNINDENT
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.UNINDENT
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.sp
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Calls:
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.INDENT 0.0
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.INDENT 2.0
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.IP \(bu 2
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\fBrun()\fP
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.UNINDENT
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.INDENT 2.0
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.UNINDENT
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.INDENT 2.0
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.UNINDENT
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.UNINDENT
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.sp
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Touches:
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.INDENT 0.0
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.INDENT 2.0
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.IP \(bu 2
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\fBfock_matrix_ao_alpha\fP
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.IP \(bu 2
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\fBfock_matrix_ao_alpha\fP
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.UNINDENT
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.INDENT 2.0
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.IP \(bu 2
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\fBmo_coef\fP
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.IP \(bu 2
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\fBlevel_shift\fP
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.UNINDENT
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.INDENT 2.0
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.IP \(bu 2
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\fBmo_coef\fP
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.IP \(bu 2
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\fBread_wf\fP
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.UNINDENT
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.SH AUTHOR
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A. Scemama, E. Giner
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.SH COPYRIGHT
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2019, A. Scemama, E. Giner
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.\" Generated by docutils manpage writer.
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