2019-01-25 11:39:31 +01:00
|
|
|
.. _cis:
|
|
|
|
|
|
|
|
|
|
.. program:: cis
|
|
|
|
|
|
|
|
|
|
===
|
|
|
|
|
cis
|
|
|
|
|
===
|
|
|
|
|
|
|
|
|
|
|
2019-01-25 14:54:22 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Configuration Interaction with Single excitations.
|
|
|
|
|
|
2019-01-25 11:39:31 +01:00
|
|
|
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:
|
|
|
|
|
|
|
|
|
|
|
2019-01-29 15:40:00 +01:00
|
|
|
1. Ground state calculation
|
2019-01-25 11:39:31 +01:00
|
|
|
|
2019-01-29 15:40:00 +01:00
|
|
|
To be sure to have the lowest |SCF| solution, perform an :ref:`scf`
|
|
|
|
|
(see the :ref:`module_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.
|
2019-01-25 11:39:31 +01:00
|
|
|
|
|
|
|
|
|
2019-01-29 15:40:00 +01:00
|
|
|
2. Excited states calculations
|
2019-01-25 14:54:22 +01:00
|
|
|
|
2019-01-29 15:40:00 +01:00
|
|
|
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.
|
2019-01-25 11:39:31 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
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.
|
|
|
|
|
|
2019-01-25 14:54:22 +01:00
|
|
|
.. note::
|
2019-01-25 11:39:31 +01:00
|
|
|
|
|
|
|
|
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`
|
