# generate_trip_determinants Subroutine

## private subroutine generate_trip_determinants(ilut_list, space_size, only_keep_conn)

### Arguments

Type IntentOptional Attributes Name
integer(kind=n_int), intent(inout) :: ilut_list(0:,:)
integer, intent(inout) :: space_size
logical, intent(in) :: only_keep_conn

## Source Code

    subroutine generate_trip_determinants(ilut_list, space_size, only_keep_conn)
! Generate a list of all singles, doubles and triples
integer(n_int), intent(inout) :: ilut_list(0:, :)
integer, intent(inout) :: space_size
logical, intent(in) :: only_keep_conn

integer :: i, j, k
integer :: a, b, c
integer :: ex(2, 3), nI(nel)
integer(n_int) :: ilut_ex(0:NifTot)
HElement_t(dp) :: HEl
! add all triples of the HF
! enumerate them as follows: take three electrons i,j,k
! with i>j>k
! then, pick three (unocc) orbitals a,b,c with a>b>c
! => triple excitation
do i = 1, nel
ex(1, 1) = HFDet(i)
do j = 1, i - 1
ex(1, 2) = HFDet(j)
do k = 1, j - 1
ex(1, 3) = HFDet(k)
do a = 1, nBasis
! for the target orbs, only take unoccupied
if (IsNotOcc(ilutHF, a)) then
ex(2, 3) = a
do b = 1, a - 1
if (IsNotOcc(ilutHF, b)) then
ex(2, 2) = b
do c = 1, b - 1
if (IsNotOcc(ilutHF, c)) then
ex(2, 1) = c
! create the triple excitation with these elecs/orbs
ilut_ex = make_ilutJ(ilutHF, ex, 3)
! if enabled, only keep connected determinants
if (only_keep_conn) then
HEl = get_helement(HFDet, nI, ilutHF, ilut_ex)
if (abs(HEl) < eps) cycle
end if

! definitely keep only determinants in the same symmetry-sector
if (.not. IsSymAllowedExcitMat(ex, 3)) cycle
call decode_bit_det(nI, ilut_ex)