subroutine htilde_mu_mat_opt_bi_ortho_tot(key_j, key_i, Nint, htot)
 implicit none
  BEGIN_DOC
  !
  ! <key_j | H_tilde | key_i> where |key_j> is developed on the LEFT basis and |key_i> is developed on the RIGHT basis
  !!
  ! Returns the total matrix element 
  !! WARNING !!
  ! 
  ! Non hermitian !!
  !
  END_DOC

  use bitmasks
 integer,           intent(in) :: Nint
 integer(bit_kind), intent(in) :: key_i(Nint,2), key_j(Nint,2)
 double precision, intent(out) :: htot
 double precision :: hmono, htwoe, hthree
 call htilde_mu_mat_opt_bi_ortho(key_j, key_i, Nint, hmono, htwoe, hthree, htot)
end
subroutine htilde_mu_mat_opt_bi_ortho(key_j, key_i, Nint, hmono, htwoe, hthree, htot)
  BEGIN_DOC
  !
  ! <key_j | H_tilde | key_i> where |key_j> is developed on the LEFT basis and |key_i> is developed on the RIGHT basis
  !!
  ! Returns the detail of the matrix element in terms of single, two and three electron contribution. 
  !! WARNING !!
  ! 
  ! Non hermitian !!
  !
  END_DOC

  use bitmasks

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

  hmono  = 0.d0
  htwoe  = 0.d0
  htot   = 0.d0
  hthree = 0.D0

  call get_excitation_degree(key_i, key_j, degree, Nint)
  if(degree.gt.2) return

  if(degree == 0)then
    call diag_htilde_mu_mat_fock_bi_ortho  (Nint, key_i, hmono, htwoe, hthree, htot)
  else if (degree == 1)then
    call single_htilde_mu_mat_fock_bi_ortho(Nint,key_j, key_i , hmono, htwoe, hthree, htot)
  else if(degree == 2)then
    call double_htilde_mu_mat_fock_bi_ortho(Nint, key_j, key_i, hmono, htwoe, hthree, htot)
  endif

  if(degree==0) then
    htot += nuclear_repulsion
  endif
 
end

! ---

subroutine htilde_mu_mat_opt_bi_ortho_no_3e(key_j, key_i, Nint, htot)

  BEGIN_DOC
  !
  ! <key_j | H_tilde | key_i> where |key_j> is developed on the LEFT basis and |key_i> is developed on the RIGHT basis
  !!
  ! Returns the detail of the matrix element WITHOUT ANY CONTRIBUTION FROM THE THREE ELECTRON TERMS 
  !! WARNING !!
  ! 
  ! Non hermitian !!
  !
  END_DOC

  use bitmasks

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

  htot   = 0.d0

  call get_excitation_degree(key_i, key_j, degree, Nint)
  if(degree.gt.2) return

  if(degree == 0)then
    call diag_htilde_mu_mat_fock_bi_ortho_no_3e(Nint, key_i,htot)
  else if (degree == 1)then
    call single_htilde_mu_mat_fock_bi_ortho_no_3e(Nint,key_j, key_i , htot)
  else if(degree == 2)then
    call double_htilde_mu_mat_fock_bi_ortho_no_3e(Nint, key_j, key_i, htot)
  endif

  if(degree==0) then
    htot += nuclear_repulsion
  endif
 
end

! ---