quantum_package/src/MRCC/mrcc_utils.irp.f

BEGIN_PROVIDER [ double precision, lambda_mrcc, (N_states,psi_det_size) ]
 implicit none
 BEGIN_DOC
 ! cm/<Psi_0|H|D_m>
 END_DOC
 integer :: i,k
 double precision :: ihpsi(N_states)
 do i=1,N_det_non_cas
   call i_h_psi(psi_non_cas(1,1,i), psi_cas, psi_cas_coef, N_int, N_det_cas, &
     size(psi_cas_coef,1), n_states, ihpsi)
   double precision :: hij
   do k=1,N_states
     if (dabs(ihpsi(k)) > 1.d-5) then
       lambda_mrcc(k,i) = psi_non_cas_coef(i,k)/ihpsi(k)
       lambda_mrcc(k,i) = min( lambda_mrcc (k,i),0.d0 )
     else
       lambda_mrcc(k,i) = 0.d0
     endif
   enddo
 enddo
END_PROVIDER



BEGIN_PROVIDER [ character*(32), dressing_type ]
 implicit none
 BEGIN_DOC
 ! [ Simple | MRCC ]
 END_DOC
 dressing_type = "MRCC"
END_PROVIDER

BEGIN_PROVIDER [ double precision, delta_ij_non_cas, (N_det_non_cas, N_det_non_cas,N_states) ]
 implicit none
 BEGIN_DOC
 ! Dressing matrix in SD basis
 END_DOC
 delta_ij_non_cas = 0.d0
 call H_apply_mrcc_simple(delta_ij_non_cas,N_det_non_cas)
END_PROVIDER

BEGIN_PROVIDER [ double precision, delta_ij, (N_det,N_det,N_states) ]
 implicit none
 BEGIN_DOC
 ! Dressing matrix in N_det basis
 END_DOC
 integer :: i,j,m
 delta_ij = 0.d0
 if (dressing_type == "MRCC") then
   call H_apply_mrcc(delta_ij,N_det)
 else if (dressing_type == "Simple") then
   do m=1,N_states
    do j=1,N_det_non_cas
     do i=1,N_det_non_cas
       delta_ij(idx_non_cas(i),idx_non_cas(j),m) = delta_ij_non_cas(i,j,m) 
     enddo
    enddo
   enddo
 endif
END_PROVIDER

BEGIN_PROVIDER [ double precision, h_matrix_dressed, (N_det,N_det) ]
 implicit none
 BEGIN_DOC
 ! Dressed H with Delta_ij
 END_DOC
 integer                        :: i, j
 do j=1,N_det
   do i=1,N_det
     h_matrix_dressed(i,j) = h_matrix_all_dets(i,j) + delta_ij(i,j,1)
   enddo
 enddo

END_PROVIDER


 BEGIN_PROVIDER [ double precision, CI_electronic_energy_dressed, (N_states_diag) ]
&BEGIN_PROVIDER [ double precision, CI_eigenvectors_dressed, (N_det,N_states_diag) ]
&BEGIN_PROVIDER [ double precision, CI_eigenvectors_s2_dressed, (N_states_diag) ]
  implicit none
  BEGIN_DOC
  ! Eigenvectors/values of the CI matrix
  END_DOC
  integer                        :: i,j
  
  do j=1,N_states_diag
    do i=1,N_det
      CI_eigenvectors_dressed(i,j) = psi_coef(i,j)
    enddo
  enddo
  
  if (diag_algorithm == "Davidson") then
    
    stop 'use Lapack'
!    call davidson_diag(psi_det,CI_eigenvectors_dressed,CI_electronic_energy_dressed, &
!        size(CI_eigenvectors_dressed,1),N_det,N_states_diag,N_int,output_determinants)
    
  else if (diag_algorithm == "Lapack") then
    
    double precision, allocatable  :: eigenvectors(:,:), eigenvalues(:)
    allocate (eigenvectors(size(H_matrix_dressed,1),N_det))
    allocate (eigenvalues(N_det))
    call lapack_diag(eigenvalues,eigenvectors,                       &
        H_matrix_dressed,size(H_matrix_dressed,1),N_det)
    CI_electronic_energy_dressed(:) = 0.d0
    do i=1,N_det
       CI_eigenvectors_dressed(i,1) = eigenvectors(i,1)
    enddo
    integer :: i_state
    double precision :: s2
    i_state = 0
    do j=1,N_det
      call get_s2_u0(psi_det,eigenvectors(1,j),N_det,N_det,s2)
      if(dabs(s2-expected_s2).le.0.3d0)then
       i_state += 1
       do i=1,N_det
         CI_eigenvectors_dressed(i,i_state) = eigenvectors(i,j)
       enddo
       CI_electronic_energy_dressed(i_state) = eigenvalues(j)
       CI_eigenvectors_s2_dressed(i_state) = s2
      endif
      if (i_state.ge.N_states_diag) then
        exit
      endif
    enddo
    deallocate(eigenvectors,eigenvalues)
  endif
  
END_PROVIDER

BEGIN_PROVIDER [ double precision, CI_energy_dressed, (N_states_diag) ]
  implicit none
  BEGIN_DOC
  ! N_states lowest eigenvalues of the dressed CI matrix
  END_DOC
  
  integer                        :: j
  character*(8)                  :: st
  call write_time(output_determinants)
  do j=1,N_states_diag
    CI_energy_dressed(j) = CI_electronic_energy_dressed(j) + nuclear_repulsion
  enddo

END_PROVIDER

subroutine diagonalize_CI_dressed
  implicit none
  BEGIN_DOC
!  Replace the coefficients of the CI states by the coefficients of the 
!  eigenstates of the CI matrix
  END_DOC
  integer :: i,j
  do j=1,N_states_diag
    do i=1,N_det
      psi_coef(i,j) = CI_eigenvectors_dressed(i,j)
    enddo
  enddo
  SOFT_TOUCH psi_coef 

end