mirror of
https://github.com/QuantumPackage/qp2.git
synced 20241109 23:13:38 +01:00
41 lines
1.9 KiB
ReStructuredText
41 lines
1.9 KiB
ReStructuredText
============


kohn_sham_rs


============






The Rangeseparated KohnSham module performs *Restricted* KohnSham calculations (the


spatial part of the MOs is common for alpha and beta spinorbitals) where the coulomb interaction is partially treated using exact exchange.


The splitting of the interaction between long and shortrange is determined by the rangeseparation parameter :option:`ao_two_e_erf_ints mu_erf`. The longrange part of the interaction is explicitly treated with exact exchange, and the shortrange part of the interaction is treated with appropriate DFT functionals.




The Rangeseparated KohnSham in an SCF and therefore is based on the ``scf_utils`` structure.


It performs the following actions:




#. Compute/Read all the one and twoelectron integrals, and store them in memory


#. Check in the EZFIO database if there is a set of MOs. If there is, it


will read them as initial guess. Otherwise, it will create a guess.


#. Perform the SCF iterations




The definition of the Fock matrix is in :file:`kohn_sham_rs fock_matrix_rs_ks.irp.f`


For the keywords related to the SCF procedure, see the ``scf_utils`` directory where you will find all options.


The main are:


# :option:`scf_utils thresh_scf`


# :option:`scf_utils level_shift`






At each iteration, the MOs are saved in the EZFIO database. Hence, if the calculation


crashes for any unexpected reason, the calculation can be restarted by running again


the SCF with the same EZFIO database.




The `DIIS`_ algorithm is implemented, as well as the `levelshifting`_ method.


If the SCF does not converge, try again with a higher value of :option:`level_shift`.




To start a calculation from scratch, the simplest way is to remove the


``mo_basis`` directory from the EZFIO database, and run the SCF again.






.. _DIIS: https://en.wikipedia.org/w/index.php?title=DIIS


.. _levelshifting: https://doi.org/10.1002/qua.560070407






