Prediction Challenge: Simulating Rydberg Photoexcited Cyclobutanone with Surface Hopping Dynamics based on Different Electronic Structure Methods

TL;DR

This study evaluates various electronic structure methods in simulating the nonadiabatic dynamics of cyclobutanone's Rydberg state, revealing significant differences in predicted lifetimes and reaction pathways, and questioning their predictive reliability.

Contribution

It compares multiple electronic structure methods in simulating nonadiabatic dynamics, highlighting the limitations of routine methods in accurately predicting molecular behavior.

Findings

MCSCF predicts a 10 ps S2 state lifetime and rapid S1 to S0 transfer.

Other methods predict much shorter S2 lifetimes, 10-250 times less.

MCSCF indicates CO elimination dominates C2H4 formation, unlike other methods.

Abstract

This research examines the nonadiabatic dynamics of cyclobutanone after excitation into the n-3s Rydberg S2 state. It stems from our contribution to the Special Topic of the Journal of Chemical Physics to test the predictive capability of computational chemistry against unseen experimental data. Decoherence-corrected fewest-switches surface hopping (DC-FSSH) was used to simulate nonadiabatic dynamics with full and approximated nonadiabatic couplings. Several simulation sets were computed with different electronic structure methods, including a multiconfigurational wavefunction (MCSCF) specially built to describe dissociative channels, multireference semiempirical approach, time-dependent density functional theory, algebraic diagrammatic construction, and coupled cluster. MCSCF dynamics predicts a slow deactivation of the S2 state (10 ps), followed by an ultrafast population transfer from S1 to S0 (<100 fs). CO elimination (C3 channel) dominates C2H4 formation (C2 channel). These findings radically differ from the other methods, which predicted S2 lifetimes 10 to 250 times shorter and C2 channel predominance. These results suggest that routine electronic structure methods may hold low predictive power for the outcome of nonadiabatic dynamics.