We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons)
carbonyl species central to earth’s tropospheric
chemistry. Triples contributions are needed
for the vertical excitation energy (Evert
EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S1
relaxation energy (Erelax
), and (TD-)DFT suffices for the
zero-point vibration energy correction
Perturbative triples corrections deliver Evert
values close in accuracy to full iterative triples
EOM-CC calculations. The error between EOM-CCSD and triples-corrected E
vert values appears
to be systematic and can be accounted for with
scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S0 minima can be used to
calculate Evert with negligible loss in accuracy,
relegating the O(N5) expense of CCSD to only
single-point energy and excitation calculations.
This affordable protocol can be applied to all
volatile carbonyl species.
E0−0 predictions do overestimate measured
values by ∼8 kJ/mol due to a lack of triples
contribution in E
relax, but this overestimation
is systematic and the mean unsigned error is
within 4 kJ/mol once this is accounted for.
InstitutionThe University of Sydney
ORCID For Submitting Author0000-0001-6955-1167
Declaration of Conflict of InterestNo conflict of interest
Version Notes2nd version:
-Updated 0-0 best estimate table to include MSE error shift for small carbonyls, and correct dZPVE for large carbonyls. Previously dZPVE in this best estimates table was mistakenly ZPVE(TS) - ZPVE(min), not ZPVE(S1 min) - ZPVE(S0 min).