anchor.diff:          !    <D|H|D>, the diagonal Hamiltonian matrix element involving D for
           !    systems defined by integrals read in from an FCIDUMP file.
   
  -        use molecular_integrals, only: get_one_body_int_mol_nonzero, get_two_body_int_mol_nonzero
  +        use molecular_integrals, only: get_one_body_int_mol_nonzero, get_two_body_int_mol_nonzero, &
  +                                        get_two_body_exchange_pbc_int_nonzero
           use system, only: sys_t
   
           complex(p) :: hmatel
  
positive.code:                 hmatel = get_one_body_int_mol(one_e_ints, one_e_ints_im, i, a, sys)
  
                  do iel = 1, sys%nel
                      if (occ_list(iel) /= i) &
                          hmatel = hmatel &
                              + get_two_body_int_mol(coulomb_ints, coulomb_ints_im, i, occ_list(iel), a, occ_list(iel), &
                                                      sys) &
                              - get_two_body_int_mol(coulomb_ints, coulomb_ints_im, i, occ_list(iel), occ_list(iel), a, &
                                                      sys)
                  end do
              end associate
  
  
negative.code: 
      end function slater_condon0_periodic_orb_list_complex
  
      pure function slater_condon1_periodic_complex(sys, occ_list, i, a, perm) result(hmatel)
  
          ! In:
  