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130 lines
3.2 KiB
Groff
130 lines
3.2 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "CISD" "1" "Jun 15, 2019" "2.0" "Quantum Package"
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.SH NAME
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cisd \- | Quantum Package >
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.nr rst2man-indent-level 0
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level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
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..
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.de1 INDENT
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.\" .rstReportMargin pre:
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. RS \\$1
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. nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin]
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. nr rst2man-indent-level +1
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.\" .rstReportMargin post:
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..
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.de UNINDENT
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. RE
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.\" indent \\n[an-margin]
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.\" old: \\n[rst2man-indent\\n[rst2man-indent-level]]
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.nr rst2man-indent-level -1
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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 and Double excitations.
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.sp
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This program takes a reference Slater determinant of ROHF\-like occupancy,
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.sp
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and performs all single and double excitations on top of it, disregarding
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spatial symmetry and compute the “n_states” lowest eigenstates of that CI
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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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.INDENT 0.0
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.IP \(bu 2
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\fBGround state calculation\fP: if even after a \fBcis()\fP calculation, natural
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orbitals (see \fBsave_natorb()\fP) and then \fBscf()\fP optimization, you are not sure to have the lowest scf
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solution,
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do the same strategy with the \fBcisd()\fP executable instead of the \fBcis()\fP\ exectuable to generate the natural
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orbitals as a guess for the \fBscf()\fP\&.
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.IP \(bu 2
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\fBExcited states calculations\fP: the lowest excited states are much likely to
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be dominanted by single\- or double\-excitations.
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Therefore, running a \fBcisd()\fP will save the “n_states” lowest states within
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the CISD space
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in the \fI\%EZFIO\fP directory, which can afterward be used as guess wave functions
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for a further multi\-state fci calculation if you specify “read_wf” = True
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before running the fci executable (see \fBdeterminants read_wf\fP).
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Also, if you specify “s2_eig” = True, the cisd will only retain states
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having the good value S^2 value
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(see \fBdeterminants expected_s2\fP and \fBdeterminants s2_eig\fP).
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If “s2_eig” = False, it will take the lowest n_states, whatever
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multiplicity they are.
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.sp
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Note: if you would like to discard some orbitals, use
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qp_set_mo_class to specify:
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.INDENT 2.0
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.IP \(bu 2
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“core” orbitals which will be always doubly occupied
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.IP \(bu 2
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“act” orbitals where an electron can be either excited from or to
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.IP \(bu 2
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“del” orbitals which will be never occupied
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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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