QuantumPackage/plugins/local/slater_tc/slater_tc_opt_single.irp.f

! ---

subroutine  single_htilde_mu_mat_fock_bi_ortho(Nint, key_j, key_i, hmono, htwoe, hthree, htot)

  BEGIN_DOC
  !
  ! <key_j |H_tilde | key_i> for single excitation ONLY FOR ONE- AND TWO-BODY TERMS 
  !!
  !! WARNING !!
  ! 
  ! Non hermitian !!
  !
  END_DOC

  use bitmasks

  implicit none
  integer,           intent(in) :: Nint
  integer(bit_kind), intent(in) :: key_j(Nint,2), key_i(Nint,2)
  double precision, intent(out) :: hmono, htwoe, hthree, htot

  integer                       :: occ(Nint*bit_kind_size,2)
  integer                       :: Ne(2), i, j, ii, jj, ispin, jspin, k, kk
  integer                       :: degree,exc(0:2,2,2)
  integer                       :: h1, p1, h2, p2, s1, s2
  double precision              :: get_mo_two_e_integral_tc_int, phase
  double precision              :: direct_int, exchange_int_12, exchange_int_23, exchange_int_13
  integer                       :: other_spin(2)
  integer(bit_kind)             :: key_j_core(Nint,2), key_i_core(Nint,2)

  other_spin(1) = 2
  other_spin(2) = 1

  hmono  = 0.d0
  htwoe  = 0.d0
  hthree = 0.d0
  htot   = 0.d0

  call get_excitation_degree(key_i, key_j, degree, Nint)
  if(degree .ne. 1) then
    return
  endif

  call bitstring_to_list_ab(key_i, occ, Ne, Nint)
  call get_single_excitation(key_i, key_j, exc, phase, Nint)
  call decode_exc(exc, 1, h1, p1, h2, p2, s1, s2)
  call get_single_excitation_from_fock_tc(Nint, key_i, key_j, h1, p1, s1, phase, hmono, htwoe, hthree, htot)

end

! ---

subroutine get_single_excitation_from_fock_tc(Nint, key_i, key_j, h, p, spin, phase, hmono, htwoe, hthree, htot)

  use bitmasks

  implicit none
  integer,           intent(in)  :: Nint
  integer,           intent(in)  :: h, p, spin
  double precision,  intent(in)  :: phase
  integer(bit_kind), intent(in)  :: key_i(Nint,2), key_j(Nint,2)
  double precision,  intent(out) :: hmono, htwoe, hthree, htot

  integer(bit_kind)              :: differences(Nint,2)
  integer(bit_kind)              :: hole(Nint,2)
  integer(bit_kind)              :: partcl(Nint,2)
  integer                        :: occ_hole(Nint*bit_kind_size,2)
  integer                        :: occ_partcl(Nint*bit_kind_size,2)
  integer                        :: n_occ_ab_hole(2),n_occ_ab_partcl(2)
  integer                        :: i0,i
  double precision               :: buffer_c(mo_num),buffer_x(mo_num)

  do i = 1, mo_num
    buffer_c(i) = tc_2e_3idx_coulomb_integrals (i,p,h)
    buffer_x(i) = tc_2e_3idx_exchange_integrals(i,p,h)
  enddo

  do i = 1, Nint
    differences(i,1) = xor(key_i(i,1), ref_closed_shell_bitmask(i,1))
    differences(i,2) = xor(key_i(i,2), ref_closed_shell_bitmask(i,2))
    hole       (i,1) = iand(differences(i,1), ref_closed_shell_bitmask(i,1))
    hole       (i,2) = iand(differences(i,2), ref_closed_shell_bitmask(i,2))
    partcl     (i,1) = iand(differences(i,1), key_i(i,1))
    partcl     (i,2) = iand(differences(i,2), key_i(i,2))
  enddo

  call bitstring_to_list_ab(hole, occ_hole, n_occ_ab_hole, Nint)
  call bitstring_to_list_ab(partcl, occ_partcl, n_occ_ab_partcl, Nint)
  hmono = mo_bi_ortho_tc_one_e(p,h)
  htwoe = fock_op_2_e_tc_closed_shell(p,h)

  ! holes :: direct terms
  do i0 = 1, n_occ_ab_hole(1)
    i = occ_hole(i0,1)
    htwoe -= buffer_c(i)
  enddo
  do i0 = 1, n_occ_ab_hole(2)
    i = occ_hole(i0,2)
    htwoe -= buffer_c(i)
  enddo
 
  ! holes :: exchange terms
  do i0 = 1, n_occ_ab_hole(spin)
    i = occ_hole(i0,spin)
    htwoe += buffer_x(i)
  enddo
 
  ! particles :: direct terms
  do i0 = 1, n_occ_ab_partcl(1)
    i = occ_partcl(i0,1)
    htwoe += buffer_c(i)
  enddo
  do i0 = 1, n_occ_ab_partcl(2)
    i = occ_partcl(i0,2)
    htwoe += buffer_c(i)
  enddo
 
  ! particles :: exchange terms
  do i0 = 1, n_occ_ab_partcl(spin)
    i = occ_partcl(i0,spin)
    htwoe -= buffer_x(i)
  enddo

  hthree = 0.d0
  if (three_body_h_tc .and. elec_num.gt.2 .and. three_e_4_idx_term) then
    call three_comp_fock_elem(Nint, key_i, h, p, spin, hthree)
  endif

  htwoe  = htwoe * phase
  hmono  = hmono * phase
  hthree = hthree * phase
  htot   = htwoe + hmono + hthree

end

! ---

subroutine three_comp_fock_elem(Nint, key_i, h_fock, p_fock, ispin_fock, hthree)

  implicit none
  integer,           intent(in)  :: Nint
  integer,           intent(in)  :: h_fock, p_fock, ispin_fock
  integer(bit_kind), intent(in)  :: key_i(Nint,2)
  double precision,  intent(out) :: hthree

  integer                        :: nexc(2),i,ispin,na,nb
  integer(bit_kind)              :: hole(Nint,2)
  integer(bit_kind)              :: particle(Nint,2)
  integer                        :: occ_hole(Nint*bit_kind_size,2)
  integer                        :: occ_particle(Nint*bit_kind_size,2)
  integer                        :: n_occ_ab_hole(2),n_occ_ab_particle(2)
  integer(bit_kind)              :: det_tmp(Nint,2)

  nexc(1) = 0
  nexc(2) = 0

  !! Get all the holes and particles of key_i with respect to the ROHF determinant
  do i = 1, Nint
    hole(i,1)     = xor(key_i(i,1),ref_bitmask(i,1))
    hole(i,2)     = xor(key_i(i,2),ref_bitmask(i,2))
    particle(i,1) = iand(hole(i,1),key_i(i,1))
    particle(i,2) = iand(hole(i,2),key_i(i,2))
    hole(i,1)     = iand(hole(i,1),ref_bitmask(i,1))
    hole(i,2)     = iand(hole(i,2),ref_bitmask(i,2))
    nexc(1)       = nexc(1) + popcnt(hole(i,1))
    nexc(2)       = nexc(2) + popcnt(hole(i,2))
  enddo

  integer                        :: tmp(2)
  !DIR$ FORCEINLINE
  call bitstring_to_list_ab(particle, occ_particle, tmp, Nint)
  ASSERT (tmp(1) == nexc(1)) ! Number of particles alpha
  ASSERT (tmp(2) == nexc(2)) ! Number of particle beta 
  !DIR$ FORCEINLINE
  call bitstring_to_list_ab(hole, occ_hole, tmp, Nint)
  ASSERT (tmp(1) == nexc(1)) ! Number of holes alpha
  ASSERT (tmp(2) == nexc(2)) ! Number of holes beta 

  !! Initialize the matrix element with the reference ROHF Slater determinant Fock element
  if(ispin_fock==1)then
   hthree = fock_a_tot_3e_bi_orth(p_fock,h_fock) 
  else 
   hthree = fock_b_tot_3e_bi_orth(p_fock,h_fock) 
  endif
  det_tmp = ref_bitmask
  do ispin=1,2
    na = elec_num_tab(ispin)
    nb = elec_num_tab(iand(ispin,1)+1)
    do i = 1, nexc(ispin)
      !DIR$ FORCEINLINE
      call fock_ac_tc_operator( occ_particle(i,ispin), ispin, det_tmp, h_fock,p_fock, ispin_fock, hthree, Nint, na, nb)
      !DIR$ FORCEINLINE
      call fock_a_tc_operator ( occ_hole    (i,ispin), ispin, det_tmp, h_fock,p_fock, ispin_fock, hthree, Nint, na, nb)
    enddo
  enddo

end

! ---

subroutine fock_ac_tc_operator(iorb,ispin,key, h_fock,p_fock, ispin_fock,hthree,Nint,na,nb)
  use bitmasks
  implicit none
  BEGIN_DOC
  ! Routine that computes the contribution to the three-electron part of the Fock operator 
  !
  ! a^dagger_{p_fock} a_{h_fock} of spin ispin_fock
  ! 
  ! on top of a determinant 'key' on which you ADD an electron of spin ispin in orbital iorb
  ! 
  ! in output, the determinant key is changed by the ADDITION of that electron 
  !
  ! the output hthree is INCREMENTED
  END_DOC
  integer, intent(in)              :: iorb, ispin, Nint, h_fock,p_fock, ispin_fock
  integer, intent(inout)           :: na, nb
  integer(bit_kind), intent(inout) :: key(Nint,2)
  double precision, intent(inout)  :: hthree

  integer                        :: occ(Nint*bit_kind_size,2)
  integer                        :: other_spin
  integer                        :: k,l,i,jj,j
  double precision :: direct_int, exchange_int
  

  if (iorb < 1) then
    print *,  irp_here, ': iorb < 1'
    print *,  iorb, mo_num
    stop -1
  endif
  if (iorb > mo_num) then
    print *,  irp_here, ': iorb > mo_num'
    print *,  iorb, mo_num
    stop -1
  endif

  ASSERT (ispin > 0)
  ASSERT (ispin < 3)
  ASSERT (Nint > 0)

  integer                        :: tmp(2)
  !DIR$ FORCEINLINE
  call bitstring_to_list_ab(key, occ, tmp, Nint)
  ASSERT (tmp(1) == elec_alpha_num)
  ASSERT (tmp(2) == elec_beta_num)

  k = shiftr(iorb-1,bit_kind_shift)+1
  ASSERT (k >0)
  l = iorb - shiftl(k-1,bit_kind_shift)-1
  ASSERT (l >= 0)
  key(k,ispin) = ibset(key(k,ispin),l)
  other_spin = iand(ispin,1)+1


  !! spin of other electrons == ispin 
  if(ispin == ispin_fock)then
   !! in what follows :: jj == other electrons in the determinant 
   !!                 :: iorb == electron that has been added of spin ispin
   !!                 :: p_fock, h_fock == hole particle of spin ispin_fock
   !! jj = ispin = ispin_fock >> pure parallel spin
   do j = 1, na
    jj = occ(j,ispin)
    hthree += three_e_single_parrallel_spin_prov(jj,iorb,p_fock,h_fock)
   enddo
   !! spin of jj == other spin than ispin AND ispin_fock
   !! exchange between the iorb and (h_fock, p_fock)
   do j = 1, nb
    jj = occ(j,other_spin) 
    direct_int = three_e_4_idx_direct_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    ! TODO
    ! use transpose
    exchange_int = three_e_4_idx_exch13_bi_ort(iorb,jj,p_fock,h_fock) ! USES 4-IDX TENSOR 
    hthree += direct_int - exchange_int
   enddo
  else !! ispin NE to ispin_fock
   !! jj = ispin BUT NON EQUAL TO ispin_fock 
   !! exchange between the jj and iorb
   do j = 1, na
    jj = occ(j,ispin)
    direct_int   = three_e_4_idx_direct_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    exchange_int = three_e_4_idx_exch23_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    hthree += direct_int - exchange_int
   enddo
   !! jj = other_spin than ispin BUT jj == ispin_fock
   !! exchange between jj and (h_fock,p_fock)
   do j = 1, nb
    jj = occ(j,other_spin) 
    direct_int = three_e_4_idx_direct_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    exchange_int = three_e_4_idx_exch13_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    hthree += direct_int - exchange_int
   enddo
  endif

  na = na+1
end

subroutine fock_a_tc_operator(iorb,ispin,key, h_fock,p_fock, ispin_fock,hthree,Nint,na,nb)
  use bitmasks
  implicit none
  BEGIN_DOC
  ! Routine that computes the contribution to the three-electron part of the Fock operator 
  !
  ! a^dagger_{p_fock} a_{h_fock} of spin ispin_fock
  ! 
  ! on top of a determinant 'key' on which you REMOVE an electron of spin ispin in orbital iorb
  ! 
  ! in output, the determinant key is changed by the REMOVAL of that electron 
  !
  ! the output hthree is INCREMENTED
  END_DOC
  integer, intent(in)            :: iorb, ispin, Nint, h_fock,p_fock, ispin_fock
  integer, intent(inout)         :: na, nb
  integer(bit_kind), intent(inout) :: key(Nint,2)
  double precision, intent(inout) :: hthree
  
  double precision  :: direct_int, exchange_int
  integer                        :: occ(Nint*bit_kind_size,2)
  integer                        :: other_spin
  integer                        :: k,l,i,jj,mm,j,m
  integer                        :: tmp(2)

  ASSERT (iorb > 0)
  ASSERT (ispin > 0)
  ASSERT (ispin < 3)
  ASSERT (Nint > 0)

  k = shiftr(iorb-1,bit_kind_shift)+1
  ASSERT (k>0)
  l = iorb - shiftl(k-1,bit_kind_shift)-1
  key(k,ispin) = ibclr(key(k,ispin),l)
  other_spin = iand(ispin,1)+1

  !DIR$ FORCEINLINE
  call bitstring_to_list_ab(key, occ, tmp, Nint)
  na = na-1
  !! spin of other electrons == ispin 
  if(ispin == ispin_fock)then
   !! in what follows :: jj == other electrons in the determinant 
   !!                 :: iorb == electron that has been added of spin ispin
   !!                 :: p_fock, h_fock == hole particle of spin ispin_fock
   !! jj = ispin = ispin_fock >> pure parallel spin
   do j = 1, na
    jj = occ(j,ispin)
    hthree -= three_e_single_parrallel_spin_prov(jj,iorb,p_fock,h_fock)
   enddo
   !! spin of jj == other spin than ispin AND ispin_fock
   !! exchange between the iorb and (h_fock, p_fock)
   do j = 1, nb
    jj = occ(j,other_spin) 
    direct_int = three_e_4_idx_direct_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    ! TODO use transpose 
    exchange_int = three_e_4_idx_exch13_bi_ort(iorb,jj,p_fock,h_fock) ! USES 4-IDX TENSOR 
    hthree -= direct_int - exchange_int
   enddo
  else !! ispin NE to ispin_fock
   !! jj = ispin BUT NON EQUAL TO ispin_fock 
   !! exchange between the jj and iorb
   do j = 1, na
    jj = occ(j,ispin)
    direct_int   = three_e_4_idx_direct_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    exchange_int = three_e_4_idx_exch23_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    hthree -= direct_int - exchange_int
   enddo
   !! jj = other_spin than ispin BUT jj == ispin_fock
   !! exchange between jj and (h_fock,p_fock)
   do j = 1, nb
    jj = occ(j,other_spin) 
    direct_int = three_e_4_idx_direct_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    exchange_int = three_e_4_idx_exch13_bi_ort(jj,iorb,p_fock,h_fock) ! USES 4-IDX TENSOR 
    hthree -= direct_int - exchange_int
   enddo
  endif

end

! ---

BEGIN_PROVIDER [double precision, fock_op_2_e_tc_closed_shell, (mo_num, mo_num)]

  BEGIN_DOC
  ! Closed-shell part of the Fock operator for the TC operator
  END_DOC
 
  implicit none

  PROVIDE N_int

  integer           :: h0,p0,h,p,k0,k,i
  integer           :: n_occ_ab(2)
  integer           :: occ(N_int*bit_kind_size,2)
  integer           :: n_occ_ab_virt(2)
  integer           :: occ_virt(N_int*bit_kind_size,2)
  integer(bit_kind) :: key_test(N_int)
  integer(bit_kind) :: key_virt(N_int,2)
  double precision  :: accu
 
  fock_op_2_e_tc_closed_shell = -1000.d0
  call bitstring_to_list_ab(ref_closed_shell_bitmask, occ, n_occ_ab, N_int)

  do i = 1, N_int
    key_virt(i,1) = full_ijkl_bitmask(i)
    key_virt(i,2) = full_ijkl_bitmask(i)
    key_virt(i,1) = xor(key_virt(i,1),ref_closed_shell_bitmask(i,1))
    key_virt(i,2) = xor(key_virt(i,2),ref_closed_shell_bitmask(i,2))
  enddo
  call bitstring_to_list_ab(key_virt, occ_virt, n_occ_ab_virt, N_int)
  ! docc ---> virt single excitations
  do h0 = 1,  n_occ_ab(1)
    h = occ(h0,1)
    do p0 = 1, n_occ_ab_virt(1)
      p = occ_virt(p0,1)
      accu = 0.d0
      do k0 = 1, n_occ_ab(1)
        k = occ(k0,1)
        accu += 2.d0 * tc_2e_3idx_coulomb_integrals(k,p,h) - tc_2e_3idx_exchange_integrals(k,p,h)
      enddo
      fock_op_2_e_tc_closed_shell(p,h) = accu 
    enddo
  enddo
 
  do h0 = 1, n_occ_ab_virt(1)
    h = occ_virt(h0,1)
    do p0 = 1,  n_occ_ab(1)
      p = occ(p0,1)
      accu = 0.d0
      do k0 = 1, n_occ_ab(1)
        k = occ(k0,1)
        accu += 2.d0 * tc_2e_3idx_coulomb_integrals(k,p,h) - tc_2e_3idx_exchange_integrals(k,p,h)
      enddo
      fock_op_2_e_tc_closed_shell(p,h) = accu 
    enddo
  enddo
 
  ! virt ---> virt single excitations
  do h0 = 1,  n_occ_ab_virt(1)
   h=occ_virt(h0,1)
   do p0 = 1, n_occ_ab_virt(1)
    p = occ_virt(p0,1)
    accu = 0.d0
    do k0 = 1, n_occ_ab(1)
     k = occ(k0,1)
     accu += 2.d0 * tc_2e_3idx_coulomb_integrals(k,p,h) - tc_2e_3idx_exchange_integrals(k,p,h)
    enddo
    fock_op_2_e_tc_closed_shell(p,h) = accu 
   enddo
  enddo
 
  do h0 = 1, n_occ_ab_virt(1)
   h = occ_virt(h0,1)
   do p0 = 1,  n_occ_ab_virt(1)
    p=occ_virt(p0,1)
    accu = 0.d0
    do k0 = 1, n_occ_ab(1)
     k = occ(k0,1)
     accu += 2.d0 * tc_2e_3idx_coulomb_integrals(k,p,h) - tc_2e_3idx_exchange_integrals(k,p,h)
    enddo
    fock_op_2_e_tc_closed_shell(p,h) = accu 
   enddo
  enddo
 
 
  ! docc ---> docc single excitations
  do h0 = 1,  n_occ_ab(1)
   h=occ(h0,1)
   do p0 = 1, n_occ_ab(1)
    p = occ(p0,1)
    accu = 0.d0
    do k0 = 1, n_occ_ab(1)
     k = occ(k0,1)
     accu += 2.d0 * tc_2e_3idx_coulomb_integrals(k,p,h) - tc_2e_3idx_exchange_integrals(k,p,h)
    enddo
    fock_op_2_e_tc_closed_shell(p,h) = accu 
   enddo
  enddo
 
  do h0 = 1, n_occ_ab(1)
   h = occ(h0,1)
   do p0 = 1,  n_occ_ab(1)
    p=occ(p0,1)
    accu = 0.d0
    do k0 = 1, n_occ_ab(1)
     k = occ(k0,1)
     accu += 2.d0 * tc_2e_3idx_coulomb_integrals(k,p,h) - tc_2e_3idx_exchange_integrals(k,p,h)
    enddo
    fock_op_2_e_tc_closed_shell(p,h) = accu 
   enddo
  enddo

! do i = 1, mo_num
!  write(*,'(100(F10.5,X))')fock_op_2_e_tc_closed_shell(:,i)
! enddo

END_PROVIDER

! ---

subroutine  single_htilde_mu_mat_fock_bi_ortho_no_3e(Nint, key_j, key_i, htot)

  BEGIN_DOC
  ! <key_j |H_tilde | key_i> for single excitation ONLY FOR ONE- AND TWO-BODY TERMS 
  !!
  !! WARNING !!
  ! 
  ! Non hermitian !!
  END_DOC

  use bitmasks

  implicit none
  integer,           intent(in) :: Nint
  integer(bit_kind), intent(in) :: key_j(Nint,2), key_i(Nint,2)
  double precision, intent(out) :: htot

  double precision              :: hmono, htwoe
  integer                       :: occ(Nint*bit_kind_size,2)
  integer                       :: Ne(2), i, j, ii, jj, ispin, jspin, k, kk
  integer                       :: degree,exc(0:2,2,2)
  integer                       :: h1, p1, h2, p2, s1, s2
  double precision              :: get_mo_two_e_integral_tc_int, phase
  double precision              :: direct_int, exchange_int_12, exchange_int_23, exchange_int_13
  integer                       :: other_spin(2)
  integer(bit_kind)             :: key_j_core(Nint,2), key_i_core(Nint,2)

  other_spin(1) = 2
  other_spin(2) = 1

  hmono  = 0.d0
  htwoe  = 0.d0
  htot   = 0.d0
  call get_excitation_degree(key_i, key_j, degree, Nint)
  if(degree.ne.1)then
   return
  endif
  call bitstring_to_list_ab(key_i, occ, Ne, Nint)

  call get_single_excitation(key_i, key_j, exc, phase, Nint)
  call decode_exc(exc,1,h1,p1,h2,p2,s1,s2)
  call get_single_excitation_from_fock_tc_no_3e(Nint, key_i, key_j, h1, p1, s1, phase, hmono, htwoe, htot)

end

! ---

subroutine get_single_excitation_from_fock_tc_no_3e(Nint, key_i, key_j, h, p, spin, phase, hmono, htwoe, htot)

  use bitmasks

  implicit none
  integer,           intent(in) :: Nint
  integer,           intent(in) :: h, p, spin
  double precision,  intent(in) :: phase
  integer(bit_kind), intent(in) :: key_i(Nint,2), key_j(Nint,2)
  double precision, intent(out) :: hmono,htwoe,htot

  integer(bit_kind)             :: differences(Nint,2)
  integer(bit_kind)             :: hole(Nint,2)
  integer(bit_kind)             :: partcl(Nint,2)
  integer                       :: occ_hole(Nint*bit_kind_size,2)
  integer                       :: occ_partcl(Nint*bit_kind_size,2)
  integer                       :: n_occ_ab_hole(2),n_occ_ab_partcl(2)
  integer                       :: i0,i
  double precision              :: buffer_c(mo_num), buffer_x(mo_num)

  do i = 1, mo_num
    buffer_c(i) = tc_2e_3idx_coulomb_integrals(i,p,h)
    buffer_x(i) = tc_2e_3idx_exchange_integrals(i,p,h)
  enddo

  do i = 1, Nint
   differences(i,1) = xor(key_i(i,1),ref_closed_shell_bitmask(i,1))
   differences(i,2) = xor(key_i(i,2),ref_closed_shell_bitmask(i,2))
   hole(i,1) = iand(differences(i,1),ref_closed_shell_bitmask(i,1))
   hole(i,2) = iand(differences(i,2),ref_closed_shell_bitmask(i,2))
   partcl(i,1) = iand(differences(i,1),key_i(i,1))
   partcl(i,2) = iand(differences(i,2),key_i(i,2))
  enddo

  call bitstring_to_list_ab(hole, occ_hole, n_occ_ab_hole, Nint)
  call bitstring_to_list_ab(partcl, occ_partcl, n_occ_ab_partcl, Nint)
  hmono = mo_bi_ortho_tc_one_e(p,h)
  htwoe = fock_op_2_e_tc_closed_shell(p,h)

  ! holes :: direct terms
  do i0 = 1, n_occ_ab_hole(1)
    i = occ_hole(i0,1)
    htwoe -= buffer_c(i)
  enddo
  do i0 = 1, n_occ_ab_hole(2)
    i = occ_hole(i0,2)
    htwoe -= buffer_c(i)
  enddo
 
  ! holes :: exchange terms
  do i0 = 1, n_occ_ab_hole(spin)
    i = occ_hole(i0,spin)
    htwoe += buffer_x(i)
  enddo
 
  ! particles :: direct terms
  do i0 = 1, n_occ_ab_partcl(1)
    i = occ_partcl(i0,1)
    htwoe += buffer_c(i)
  enddo
  do i0 = 1, n_occ_ab_partcl(2)
    i = occ_partcl(i0,2)
    htwoe += buffer_c(i)
  enddo
 
  ! particles :: exchange terms
  do i0 = 1, n_occ_ab_partcl(spin)
    i = occ_partcl(i0,spin)
    htwoe -= buffer_x(i)
  enddo
  htwoe = htwoe * phase
  hmono = hmono * phase
  htot  = htwoe + hmono 

end


subroutine  single_htilde_mu_mat_fock_bi_ortho_no_3e_both(Nint, key_j, key_i, hji,hij)

  BEGIN_DOC
  ! <key_j |H_tilde | key_i> and <key_i |H_tilde | key_j> for single excitation ONLY FOR ONE- AND TWO-BODY TERMS 
  !!
  !! WARNING !!
  ! 
  ! Non hermitian !!
  END_DOC

  use bitmasks

  implicit none
  integer,           intent(in) :: Nint
  integer(bit_kind), intent(in) :: key_j(Nint,2), key_i(Nint,2)
  double precision, intent(out) :: hji,hij

  double precision              :: hmono, htwoe
  integer                       :: occ(Nint*bit_kind_size,2)
  integer                       :: Ne(2), i, j, ii, jj, ispin, jspin, k, kk
  integer                       :: degree,exc(0:2,2,2)
  integer                       :: h1, p1, h2, p2, s1, s2
  double precision              :: get_mo_two_e_integral_tc_int, phase
  double precision              :: direct_int, exchange_int_12, exchange_int_23, exchange_int_13
  integer                       :: other_spin(2)
  integer(bit_kind)             :: key_j_core(Nint,2), key_i_core(Nint,2)

  other_spin(1) = 2
  other_spin(2) = 1

  hmono  = 0.d0
  htwoe  = 0.d0
  hji   = 0.d0
  hij   = 0.d0
  call get_excitation_degree(key_i, key_j, degree, Nint)
  if(degree.ne.1)then
   return
  endif
  call bitstring_to_list_ab(key_i, occ, Ne, Nint)

  call get_single_excitation(key_i, key_j, exc, phase, Nint)
  call decode_exc(exc,1,h1,p1,h2,p2,s1,s2)
  call get_single_excitation_from_fock_tc_no_3e_both(Nint, key_i, key_j, h1, p1, s1, phase, hji,hij)

end

! ---

subroutine get_single_excitation_from_fock_tc_no_3e_both(Nint, key_i, key_j, h, p, spin, phase, hji,hij)

  use bitmasks

  implicit none
  integer,           intent(in) :: Nint
  integer,           intent(in) :: h, p, spin
  double precision,  intent(in) :: phase
  integer(bit_kind), intent(in) :: key_i(Nint,2), key_j(Nint,2)
  double precision, intent(out) :: hji,hij
  double precision :: hmono_ji,htwoe_ji
  double precision :: hmono_ij,htwoe_ij

  integer(bit_kind)             :: differences(Nint,2)
  integer(bit_kind)             :: hole(Nint,2)
  integer(bit_kind)             :: partcl(Nint,2)
  integer                       :: occ_hole(Nint*bit_kind_size,2)
  integer                       :: occ_partcl(Nint*bit_kind_size,2)
  integer                       :: n_occ_ab_hole(2),n_occ_ab_partcl(2)
  integer                       :: i0,i
  double precision              :: buffer_c_ji(mo_num), buffer_x_ji(mo_num)
  double precision              :: buffer_c_ij(mo_num), buffer_x_ij(mo_num)

  do i = 1, mo_num
    buffer_c_ji(i) = tc_2e_3idx_coulomb_integrals(i,p,h)
    buffer_x_ji(i) = tc_2e_3idx_exchange_integrals(i,p,h)
    buffer_c_ij(i) = tc_2e_3idx_coulomb_integrals_transp(i,p,h)
    buffer_x_ij(i) = tc_2e_3idx_exchange_integrals_transp(i,p,h)
  enddo

  do i = 1, Nint
   differences(i,1) = xor(key_i(i,1),ref_closed_shell_bitmask(i,1))
   differences(i,2) = xor(key_i(i,2),ref_closed_shell_bitmask(i,2))
   hole(i,1) = iand(differences(i,1),ref_closed_shell_bitmask(i,1))
   hole(i,2) = iand(differences(i,2),ref_closed_shell_bitmask(i,2))
   partcl(i,1) = iand(differences(i,1),key_i(i,1))
   partcl(i,2) = iand(differences(i,2),key_i(i,2))
  enddo

  call bitstring_to_list_ab(hole, occ_hole, n_occ_ab_hole, Nint)
  call bitstring_to_list_ab(partcl, occ_partcl, n_occ_ab_partcl, Nint)
  hmono_ji = mo_bi_ortho_tc_one_e(p,h)
  htwoe_ji = fock_op_2_e_tc_closed_shell(p,h)
  hmono_ij = mo_bi_ortho_tc_one_e(h,p)
  htwoe_ij = fock_op_2_e_tc_closed_shell(h,p)

  ! holes :: direct terms
  do i0 = 1, n_occ_ab_hole(1)
    i = occ_hole(i0,1)
    htwoe_ji -= buffer_c_ji(i)
    htwoe_ij -= buffer_c_ij(i)
  enddo
  do i0 = 1, n_occ_ab_hole(2)
    i = occ_hole(i0,2)
    htwoe_ji -= buffer_c_ji(i)
    htwoe_ij -= buffer_c_ij(i)
  enddo
 
  ! holes :: exchange terms
  do i0 = 1, n_occ_ab_hole(spin)
    i = occ_hole(i0,spin)
    htwoe_ji += buffer_x_ji(i)
    htwoe_ij += buffer_x_ij(i)
  enddo
 
  ! particles :: direct terms
  do i0 = 1, n_occ_ab_partcl(1)
    i = occ_partcl(i0,1)
    htwoe_ji += buffer_c_ji(i)
    htwoe_ij += buffer_c_ij(i)
  enddo
  do i0 = 1, n_occ_ab_partcl(2)
    i = occ_partcl(i0,2)
    htwoe_ji += buffer_c_ji(i)
    htwoe_ij += buffer_c_ij(i)
  enddo
 
  ! particles :: exchange terms
  do i0 = 1, n_occ_ab_partcl(spin)
    i = occ_partcl(i0,spin)
    htwoe_ji -= buffer_x_ji(i)
    htwoe_ij -= buffer_x_ij(i)
  enddo
  htwoe_ji = htwoe_ji * phase
  hmono_ji = hmono_ji * phase
  hji  = htwoe_ji + hmono_ji 

  htwoe_ij = htwoe_ij * phase
  hmono_ij = hmono_ij * phase
  hij  = htwoe_ij + hmono_ij 

end