Type | Intent | Optional | Attributes | Name | ||
---|---|---|---|---|---|---|

integer(kind=n_int), | intent(in) | :: | alpha |
|||

integer(kind=n_int), | intent(in) | :: | beta |
|||

integer, | intent(in) | :: | n_orbs |

```
function open_shell_product(alpha, beta, n_orbs) result(basis)
! compute the tensor product of alpha and beta spin-bases to give
! fully open-shell determinants, the first input is to be defined as
! the alpha spin part
! and the beta input then is only as big as n_orbs - n_alpha and only
! tells us in which empty orbitals of the alpha orbitals beta spins
! should be set
! sorting is not so easily ensured here anymore..
integer(n_int), intent(in) :: alpha, beta
integer, intent(in) :: n_orbs
integer(n_int) :: basis
integer, allocatable :: nZeros(:), nOnes(:)
integer(n_int) :: mask_zeros
integer :: i
! the setting of the alpha spins is the same or?
basis = set_alpha_beta_spins(alpha, n_orbs, .false.)
! i need the zeros, but just in the n_orbs range
mask_zeros = iand(not(alpha), int(maskr(n_orbs), n_int))
allocate(nZeros(popcnt(mask_zeros)))
call decode_bit_det(nZeros, [mask_zeros])
! now i need the ones from beta
allocate(nOnes(popcnt(beta)))
call decode_bit_det(nOnes, [beta])
! and i have to set all beta-spins indicated by nZeros(nOnes)
! so we need beta spin!
nZeros = 2 * nZeros - 1
do i = 1, size(nOnes)
basis = ibset(basis, nZeros(nOnes(i)) - 1)
end do
end function open_shell_product
```

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