mirror of
https://github.com/QuantumPackage/qp2.git
synced 2024-12-21 11:03:29 +01:00
75 lines
2.5 KiB
Fortran
75 lines
2.5 KiB
Fortran
|
program cisd
|
|||
|
|
implicit none
|
|||
|
|
BEGIN_DOC
|
|||
|
|
! Configuration Interaction with Single and Double excitations.
|
|||
|
|
!
|
|||
|
|
! This program takes a reference Slater determinant of ROHF-like occupancy,
|
|||
|
|
!
|
|||
|
|
! and performs all single and double excitations on top of it, disregarding
|
|||
|
|
! spatial symmetry and compute 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: if even after a :c:func:`cis` calculation, natural
|
|||
|
|
! orbitals (see :c:func:`save_natorb`) and then :c:func:`scf` optimization, you are not sure to have the lowest scf
|
|||
|
|
! solution,
|
|||
|
|
! do the same strategy with the :c:func:`cisd` executable instead of the :c:func:`cis` exectuable to generate the natural
|
|||
|
|
! orbitals as a guess for the :c:func:`scf`.
|
|||
|
|
!
|
|||
|
|
!
|
|||
|
|
!
|
|||
|
|
! * EXCITED STATES CALCULATIONS: the lowest excited states are much likely to
|
|||
|
|
! be dominanted by single- or double-excitations.
|
|||
|
|
! Therefore, running a :c:func:`cisd` will save the "n_states" lowest states within
|
|||
|
|
! the CISD space
|
|||
|
|
! in the EZFIO folder, which can afterward be used as guess wave functions
|
|||
|
|
! for a further multi-state fci calculation if you specify "read_wf" = True
|
|||
|
|
! before running the fci executable (see :option:`determinants read_wf`).
|
|||
|
|
! Also, if you specify "s2_eig" = True, the cisd will only retain states
|
|||
|
|
! having the good value :math:`S^2` value
|
|||
|
|
! (see :option:`determinants expected_s2` and :option:`determinants s2_eig`).
|
|||
|
|
! If "s2_eig" = False, it will take the lowest n_states, whatever
|
|||
|
|
! multiplicity they are.
|
|||
|
|
!
|
|||
|
|
!
|
|||
|
|
!
|
|||
|
|
! Note: if you would like to discard some orbitals, use
|
|||
|
|
! :ref:`qp_set_mo_class` 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
|
|||
|
|
END_DOC
|
|||
|
|
read_wf = .False.
|
|||
|
|
SOFT_TOUCH read_wf
|
|||
|
|
call run
|
|||
|
|
end
|
|||
|
|
|
|||
|
|
subroutine run
|
|||
|
|
implicit none
|
|||
|
|
integer :: i
|
|||
|
|
|
|||
|
|
call H_apply_cisd
|
|||
|
|
print *, 'N_det = ', N_det
|
|||
|
|
print*,'******************************'
|
|||
|
|
print *, 'Energies of the states:'
|
|||
|
|
do i = 1,N_states
|
|||
|
|
print *, i, CI_energy(i)
|
|||
|
|
enddo
|
|||
|
|
if (N_states > 1) then
|
|||
|
|
print*,'******************************'
|
|||
|
|
print*,'Excitation energies '
|
|||
|
|
do i = 2, N_states
|
|||
|
|
print*, i ,CI_energy(i) - CI_energy(1)
|
|||
|
|
enddo
|
|||
|
|
endif
|
|||
|
|
psi_coef = ci_eigenvectors
|
|||
|
|
SOFT_TOUCH psi_coef
|
|||
|
|
call save_wavefunction
|
|||
|
|
call ezfio_set_cisd_energy(CI_energy)
|
|||
|
|
|
|||
|
|
end
|