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

type(rdm_spawn_t), | intent(inout) | :: | spawn |
|||

integer, | intent(in) | :: | nI(nel) |
|||

real(kind=dp), | intent(in) | :: | full_sign(spawn%rdm_send%sign_length) |

```
subroutine fill_spawn_rdm_diag_guga(spawn, nI, full_sign)
! i have to write a routine, which correctly takes into
! account all the diagonal contributions from double excitations
type(rdm_spawn_t), intent(inout) :: spawn
integer, intent(in) :: nI(nel)
real(dp), intent(in) :: full_sign(spawn%rdm_send%sign_length)
integer :: i, s_orbs(nel), s, inc_i, j, inc_j, p
real(dp) :: occ_i, occ_j, x0, x1
! i have to figure out what exactly contributes to here..
! according to the paper about the two-RDM labels the
! diagonal elements of the 2-RDM are given by
! D_ij,kl = <psi| e_{ki,lj} | psi>
! which for the diagonal contribution kl = ij yields
! D_{ij,ij} = <psi| e_{ii,jj} |psi>
! which is definetly purely diagonal!
! i could try to use the add_to_rdm_spawn_t routine in
! rdm_data_utils with the according modified matrix elements.
i = 1
s_orbs = gtID(nI)
! TODO: I could also try to add the diagonal exchange
! contributions directly here! so this routine would be
! applicable in the stochastic spawning already
do while (i <= nel)
s = s_orbs(i)
if (isDouble(nI, i)) then
occ_i = 2.0_dp
inc_i = 2
! i think here i have to put the full diagonal
! D_{ii,ii} entry, which counts double occupancies
! and i will try for now to reuse the following routine:
! put with the spatial orbital s
! but maybe I have to also add the 'switched' indices
! contribution.. which would mean a factor of 2..
call add_to_rdm_spawn_t(spawn, s, s, s, s, occ_i * full_sign, .true.)
else
occ_i = 1.0_dp
inc_i = 1
end if
j = i + inc_i
do while (j <= nel)
p = s_orbs(j)
if (isDouble(nI, j)) then
occ_j = 2.0_dp
inc_j = 2
else
occ_j = 1.0_dp
inc_j = 1
end if
! i could also just multiply by 2 here, since this will
! get strored in the same D_{ij,ij} RDM element!
! but for now I decided to fill in all disting 2-RDM
! elements
! since here we do not have spawning this should also
! get stored symmetrically! as otherwise this will
! junk up the hermiticity error calculation!
call add_to_rdm_spawn_t(spawn, s, s, p, p, &
occ_i * occ_j * full_sign, .true.)
call add_to_rdm_spawn_t(spawn, p, p, s, s, &
occ_i * occ_j * full_sign, .true.)
! i can also add the fully diagonal exchange contributions
! here. this is also necessary to do, if I want to use
! this routine in the stochastic sampling
! but for open-shell to open-shell exchange excitations
! I have to calculate the correct x1 matrix element..
! x0 matrix element is easy
x0 = -occ_i * occ_j / 2.0_dp
if (inc_i == 1 .and. inc_j == 1) then
! if we have open-shell to open chell
x1 = calcDiagExchangeGUGA_nI(i, j, nI) / 2.0_dp
call add_to_rdm_spawn_t(spawn, s, p, p, s, &
(x0 - x1) * full_sign, .true.)
call add_to_rdm_spawn_t(spawn, p, s, s, p, &
(x0 - x1) * full_sign, .true.)
else
call add_to_rdm_spawn_t(spawn, s, p, p, s, &
x0 * full_sign, .true.)
! and the symmetric version:
call add_to_rdm_spawn_t(spawn, p, s, s, p, &
x0 * full_sign, .true.)
end if
j = j + inc_j
end do
i = i + inc_i
end do
end subroutine fill_spawn_rdm_diag_guga
```

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