quantum_package/plugins/MRCC/mrcc_utils.irp.f

BEGIN_PROVIDER [ double precision, lambda_mrcc, (N_states,psi_det_size) ]
&BEGIN_PROVIDER [ double precision, lambda_pert, (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), hij(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)
   call i_h_j(psi_non_cas(1,1,i),psi_non_cas(1,1,i),N_int,hij)
   do k=1,N_states
   lambda_pert(k,i) = 1d0 / (CI_electronic_energy(k)-hij(k))
   lambda_mrcc(k,i) = psi_non_cas_coef(i,k)/ihpsi(k)
     if ((lambda_mrcc(k,i)/lambda_pert(k,i))<0.d0 .or. (lambda_mrcc(k,i)/lambda_pert(k,i))>4.d0) then
       lambda_mrcc(k,i) = lambda_pert(k,i)
     else
       if ((lambda_mrcc(k,i)/lambda_pert(k,i))<0.1d0 .or. (lambda_mrcc(k,i)/lambda_pert(k,i))>=0d0) then
       lambda_mrcc(k,i) = lambda_mrcc(k,i)*((cos((lambda_mrcc(k,i)/lambda_pert(k,i))*3.141592653589793d0/0.1d0+3.141592653589793d0)+1d0)/2.d0) &
                          + lambda_pert(k,i)*(1.d0-((cos((lambda_mrcc(k,i)/lambda_pert(k,i))*3.141592653589793d0/0.1d0+3.141592653589793d0)+1.d0)/2.d0))
       elseif ((lambda_mrcc(k,i)/lambda_pert(k,i))<=4.0d0 .or. (lambda_mrcc(k,i)/lambda_pert(k,i))>2.0d0) then
       lambda_mrcc(k,i) = lambda_mrcc(k,i)*(1.d0-(cos(abs(2.d0-(lambda_mrcc(k,i)/lambda_pert(k,i)))*3.141592653589793d0/2.0d0+3.141592653589793d0)+1.d0)/2d0) &
                          + lambda_pert(k,i)*((cos(abs(2.d0-(lambda_mrcc(k,i)/lambda_pert(k,i)))*3.141592653589793d0/2.0d0+3.141592653589793d0)+1.d0)/2.d0)
       else
       lambda_mrcc(k,i) = lambda_mrcc(k,i)
       endif
     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
    
    integer :: istate
    istate = 1
    call davidson_diag_mrcc(psi_det,CI_eigenvectors_dressed,CI_electronic_energy_dressed, &
        size(CI_eigenvectors_dressed,1),N_det,N_states_diag,N_int,output_determinants,istate)
    
  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
    if (s2_eig) then
      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
    else
      do j=1,N_states_diag
        call get_s2_u0(psi_det,eigenvectors(1,j),N_det,N_det,s2)
        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
      enddo
    endif
    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