mirror of
https://github.com/QuantumPackage/qp2.git
synced 2024-11-03 12:43:48 +01:00
74 lines
2.4 KiB
Groff
74 lines
2.4 KiB
Groff
.\" Man page generated from reStructuredText.
|
||
.
|
||
.TH "EXCITED_STATES" "1" "Jun 15, 2019" "2.0" "Quantum Package"
|
||
.SH NAME
|
||
excited_states \- | Quantum Package >
|
||
.
|
||
.nr rst2man-indent-level 0
|
||
.
|
||
.de1 rstReportMargin
|
||
\\$1 \\n[an-margin]
|
||
level \\n[rst2man-indent-level]
|
||
level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
|
||
-
|
||
\\n[rst2man-indent0]
|
||
\\n[rst2man-indent1]
|
||
\\n[rst2man-indent2]
|
||
..
|
||
.de1 INDENT
|
||
.\" .rstReportMargin pre:
|
||
. RS \\$1
|
||
. nr rst2man-indent\\n[rst2man-indent-level] \\n[an-margin]
|
||
. nr rst2man-indent-level +1
|
||
.\" .rstReportMargin post:
|
||
..
|
||
.de UNINDENT
|
||
. RE
|
||
.\" indent \\n[an-margin]
|
||
.\" old: \\n[rst2man-indent\\n[rst2man-indent-level]]
|
||
.nr rst2man-indent-level -1
|
||
.\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
|
||
.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
|
||
..
|
||
.sp
|
||
It is possible to run excited states calculations with the quantum
|
||
package. To do this, set \fBdeterminants n_states\fP to the number
|
||
of requested states. The selection criterion will be the maximum of the
|
||
selection criteria for each state. If the Davidson diagonalization has
|
||
difficulties to converge, increase the \fBdavidson n_states_diag\fP
|
||
value.
|
||
.sp
|
||
When computing multiple states, it is good to have the
|
||
\fBdeterminants s2_eig\fP flag \fBtrue\fP\&. This will force the Davidson
|
||
algorithm to choose only vectors with a value of \ewidehat{S^2} equal to
|
||
\fBdeterminants expected_s2\fP\&. Otherwise, different spin states
|
||
will come out in the diagonalization.
|
||
.sp
|
||
The \fIQuantum Package\fP doesn’t take account of the symmetry. Due to numerical noise,
|
||
excited states of different symmetries may enter in the calculation.
|
||
Note that it is possible to make state\-average calculation of states
|
||
with different symmetries and/or different spin multiplicities.
|
||
.sp
|
||
To include excited states of all possible symmetries, a simple trick is
|
||
to run a preliminary multi\-state CIS calculation using the CIS
|
||
program, and then running the selected FCI restarting from the CIS
|
||
states, setting \fBdeterminants read_wf\fP to \fBtrue\fP\&.
|
||
.sp
|
||
Usually, it is good practice to use state\-averaged natural MOs so that
|
||
all states have MOs of comparable quality. This allows for a faster
|
||
convergence of excitation energies.
|
||
.sp
|
||
\fBSEE ALSO:\fP
|
||
.INDENT 0.0
|
||
.INDENT 3.5
|
||
The documentation of the scf, cis and
|
||
fci programs.
|
||
.UNINDENT
|
||
.UNINDENT
|
||
.SH AUTHOR
|
||
A. Scemama, E. Giner
|
||
.SH COPYRIGHT
|
||
2019, A. Scemama, E. Giner
|
||
.\" Generated by docutils manpage writer.
|
||
.
|