mirror of
https://github.com/QuantumPackage/qp2.git
synced 2024-11-14 01:53:49 +01:00
79 lines
2.0 KiB
ReStructuredText
79 lines
2.0 KiB
ReStructuredText
|
.. _cis:
|
||
|
|
|
||
|
|
.. program:: cis
|
||
|
|
|
||
|
|
===
|
||
|
|
cis
|
||
|
|
===
|
||
|
|
|
||
|
|
|
||
|
|
This program takes a reference Slater determinant of ROHF-like
|
||
|
|
occupancy, and performs all single excitations on top of it.
|
||
|
|
Disregarding spatial symmetry, it computes the `n_states` lowest
|
||
|
|
eigenstates of that CI matrix. (see :option:`determinants n_states`)
|
||
|
|
|
||
|
|
This program can be useful in many cases:
|
||
|
|
|
||
|
|
|
||
|
|
Ground state calculation
|
||
|
|
|
||
|
|
To be sure to have the lowest |SCF| solution, perform an :ref:`.scf.`
|
||
|
|
(see the :ref:`hartree_fock` module), then a :ref:`.cis.`, save
|
||
|
|
the natural orbitals (see :ref:`.save_natorb.`) and re-run an
|
||
|
|
:ref:`.scf.` optimization from this |MO| guess.
|
||
|
|
|
||
|
|
|
||
|
|
Excited states calculations
|
||
|
|
|
||
|
|
The lowest excited states are much likely to be dominated by
|
||
|
|
single-excitations. Therefore, running a :ref:`.cis.` will save
|
||
|
|
the `n_states` lowest states within the |CIS| space in the |EZFIO|
|
||
|
|
directory, which can afterwards be used as guess wave functions for
|
||
|
|
a further multi-state |FCI| calculation if :option:`determinants
|
||
|
|
read_wf` is set to |true| before running the :ref:`.fci.`
|
||
|
|
executable.
|
||
|
|
|
||
|
|
If :option:`determinants s2_eig` is set to |true|, the |CIS|
|
||
|
|
will only retain states having the expected |S^2| value (see
|
||
|
|
:option:`determinants expected_s2`). Otherwise, the |CIS| will take
|
||
|
|
the lowest :option:`determinants n_states`, whatever multiplicity
|
||
|
|
they are.
|
||
|
|
|
||
|
|
Note
|
||
|
|
|
||
|
|
To discard some orbitals, use the :ref:`qp_set_mo_class`
|
||
|
|
command to specify:
|
||
|
|
|
||
|
|
* *core* orbitals which will be always doubly occupied
|
||
|
|
|
||
|
|
* *act* orbitals where an electron can be either excited from or to
|
||
|
|
|
||
|
|
* *del* orbitals which will be never occupied
|
||
|
|
|
||
|
|
|
||
|
|
Needs:
|
||
|
|
|
||
|
|
.. hlist::
|
||
|
|
:columns: 3
|
||
|
|
|
||
|
|
* :c:data:`read_wf`
|
||
|
|
|
||
|
|
Calls:
|
||
|
|
|
||
|
|
.. hlist::
|
||
|
|
:columns: 3
|
||
|
|
|
||
|
|
* :c:func:`run`
|
||
|
|
|
||
|
|
Touches:
|
||
|
|
|
||
|
|
.. hlist::
|
||
|
|
:columns: 3
|
||
|
|
|
||
|
|
* :c:data:`fock_matrix_ao_alpha`
|
||
|
|
* :c:data:`fock_matrix_ao_alpha`
|
||
|
|
* :c:data:`mo_coef`
|
||
|
|
* :c:data:`level_shift`
|
||
|
|
* :c:data:`mo_coef`
|
||
|
|
* :c:data:`read_wf`
|