quantum_package/plugins/CISD_SC2_selected/cisd_sc2_selection.irp.f

program cisd_sc2_selected
  implicit none
  integer                        :: i,k
  use bitmasks

  
  double precision, allocatable  :: pt2(:), norm_pert(:), H_pert_diag(:),E_old(:)
  integer                        :: N_st, iter,degree
  character*(64)                 :: perturbation
  N_st = N_states
  allocate (pt2(N_st), norm_pert(N_st), H_pert_diag(N_st),E_old(N_st))
  
  pt2 = 1.d0
  perturbation = "epstein_nesbet_sc2_projected"
                 
  E_old(1) = HF_energy
  threshold_davidson = 1.d-10
  if (N_det > N_det_max) then
    call diagonalize_CI_SC2
    call save_wavefunction
    psi_det = psi_det_sorted
    psi_coef = psi_coef_sorted
    N_det = N_det_max
    soft_touch N_det psi_det psi_coef
    call diagonalize_CI
    call save_wavefunction
    print *,  'N_det    = ', N_det
    print *,  'N_states = ', N_states
    print *,  'PT2      = ', pt2
    print *,  'E        = ', CI_SC2_energy
    print *,  'E+PT2    = ', CI_SC2_energy+pt2
    print *,  '-----'
  endif

  integer :: i_count
  i_count = 0
  do while (N_det < N_det_max.and.maxval(abs(pt2(1:N_st))) > pt2_max)
    print*,'----'
    print*,''
    call H_apply_SC2_selected(pt2, norm_pert, H_pert_diag,  N_st)
    call diagonalize_CI_SC2
    print *,  'N_det                        = ', N_det
    do i = 1, N_st
     print*,'state ',i
     print *,  'PT2(SC2)                     = ', pt2(i)
     print *,  'E(SC2)                       = ', CI_SC2_energy(i) 
     print *,  'E_before(SC2)+PT2(SC2)       = ', (E_old(i)+pt2(i)) 
     if(i==1)then
      print *,  'E(SC2)+PT2(projctd)SC2       = ', (E_old(i)+H_pert_diag(i)) 
     endif
     E_old(i) = CI_SC2_energy(i)
    enddo
     if(dabs(E_old(i) - CI_SC2_energy(i) ).le.1.d-12)then
      i_count += 1
      selection_criterion_factor = selection_criterion_factor * 0.5d0
      if(i_count > 5)then
       exit
      endif
     else 
      i_count = 0
     endif

    ! =~=~=~=~=~=~=~=~=~=~=~=~=~!
    ! W r i t e _ o n _ d i s k !
    ! =~=~=~=~=~=~=~=~=~=~=~=~=~!

    call ezfio_set_cisd_sc2_selected_energy(CI_SC2_energy(1))

  enddo
  N_det = min(N_det_max,N_det)
  threshold_davidson = 1.d-10
  touch N_det psi_det psi_coef threshold_davidson davidson_criterion
  call diagonalize_CI_SC2
  pt2 = 0.d0
 
  if(do_pt2_end)then
   threshold_selectors = 1.d0
   call H_apply_PT2(pt2, norm_pert, H_pert_diag,  N_st)
   do i = 1, N_st
    max = 0.d0
   
     print*,''
     print*,'-------------'
     print*,'for state ',i
     print*,''
     print*,'N_det = ',N_det
    do k = 1, N_det
     if(dabs(psi_coef(k,i)).gt.max)then
      max = dabs(psi_coef(k,i))
      imax = k
     endif
    enddo
    double precision :: max
    integer :: imax
    print *,  'PT2(SC2)                     = ', pt2(i)
    print *,  'E(SC2)                       = ', CI_SC2_energy(i)
    print *,  'E_before(SC2)+PT2(SC2)       = ', CI_SC2_energy(i)+pt2(i)
    print *,  'E_before(SC2)+PT2(SC2)_new   = ', CI_SC2_energy(i)+pt2(i)* (1.d0 + norm_pert) - H_pert_diag(i)
   
    print*,'Largest coefficient of the state : ',dabs(psi_coef(imax,i))
    call get_excitation_degree(ref_bitmask,psi_det(1,1,imax),degree,N_int)
    print*,'Degree of excitation of this determinant : ',degree
    
   enddo

    ! =~=~=~=~=~=~=~=~=~=~=~=~=~!
    ! W r i t e _ o n _ d i s k !
    ! =~=~=~=~=~=~=~=~=~=~=~=~=~!

    call ezfio_set_cisd_sc2_selected_energy_pt2(CI_SC2_energy(i)+pt2(i)* (1.d0 + norm_pert) - H_pert_diag(i))
  endif
  call save_wavefunction
  deallocate(pt2,norm_pert,H_pert_diag)
end