NTOs between triplet excited states

Questions
#1

Dear all,

Is it possible to obtain natural transition orbitals between triplet excited states calculated with TDA in solution?
I tried generating them with input pasted below, both with and without the “cis_state_deriv = 1” keyword, but I was only able to obtain NTOs corresponding to excitations from the ground state.

$rem
jobtype             sp
method              camb3lyp
dft_d               d3_bj
basis               def2-svp
MAX_SCF_CYCLES      500
SCF_CONVERGENCE     9
scf_final_print     true
cis_n_roots         5
cis_singlets        false
cis_triplets        true
rpa                 false
cis_moments         true
cis_relaxed_density true
cis_state_deriv     1
sts_mom             true
solvent_method      pcm
make_cube_files     true
nto_pairs           true
plots               true
iqmol_fchk          true
molden_format       true
$end

$pcm
 NonEquilibrium true
 Theory         cpcm
 StateSpecific  perturb
$end

$solvent
solventname        acetonitrile
$end

$plots
grid_points 100 100 100
transition_density 1-5
natural_transition_orbital 1-5
$end

Kind regards,
Joanna

#2

I don’t think anything like this is implemented. It issue is that the state-to-state transition moments are implemented via a “pseudo-wavefunction” approximation that is outside of proper response theory, where these couplings would require quadratic response rather than the linear response of conventional TD-DFT. So there’s no easy way to compute NTOs between excited states because the only response that you’ve computed is linear response of the ground state, which gives you ground-to-excited amplitudes and thus NTOs. Stated differently, the NTOs are natural orbitals of the transition density and you’ve only computed transition densities with respect to the ground state.

#3

I know that it works for spin-flip TDDFT. For example in Example 7.3.8, here
https://manual.q-chem.com/latest/ex_SFDFT-wfa.html

You can try something like

$rem
jobtype             sp
method              camb3lyp
dft_d               d3_bj
basis               def2-svp
MAX_SCF_CYCLES      500
SCF_CONVERGENCE     9
cis_n_roots         5
cis_singlets        false
cis_triplets        true
rpa                 false
solvent_method      pcm
nto_pairs           true
molden_format       true
state_analysis    true
wfa_ref_state     1
$end

This goes via the libwfa library, which has some enhanced options
https://manual.q-chem.com/latest/ex_StateAnal_MolDen.html