Non-adiabatic dynamics of ring opening in cyclohexa-1, 3-diene described by an ensemble density-functional theory method. (18th June 2019)

• Record Type: Journal Article
• Authors: Filatov, Michael; Min, Seung Kyu; Kim, Kwang S.
• Is Part Of: Molecular physics. Volume 117:Number 9/12(2019)
• Page Start: 1128
• Page End: 1141
• Publication Date: 2019-06-18
• Subjects: Non-adiabatic molecular dynamics -- decoherence-induced surface hopping -- ensemble density-functional theory -- conical intersections -- photochemical ring opening; Molecules -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Molécules -- Périodiques; Chimie physique et théorique -- Périodiques; 539.6.05
• DOI: 10.1080/00268976.2018.1519200
• Languages: English
• ISSNs: 0026-8976

Abstract

ABSTRACT: The dynamics of the ring opening in the S 1 state of cyclohexa-1, 3-diene (CHD) is studied by a new direct mixed quantum-classical non-adiabatic dynamics approach which employs the decoherence-induced surface hopping based on the exact factorisation (DISH-XF) molecular dynamics method in connection with the state-interaction state-averaged spin-restricted ensemble-referenced Kohn–Sham (SI-SA-REKS, or SSR) electronic structure method. The critical species on the S 0 and S 1 PESs of CHD were studied using the SSR method and the minimum energy pathways (MEPs) were optimised. The obtained vertical excitation energies are in good agreement (within ca. 5–6 kcal/mol) with the experimental values. The optimised geometry of the S 1 / S 0 minimum energy conical intersection (MECI) agrees well with the previously obtained MSPT2 geometry. The DISH-XF/SSR non-adiabatic molecular dynamics (NAMD) simulations of ring opening in CHD predict the S 1 exponential decay constant τ = 234 ± 8 fs in a reasonable agreement with an experimental estimate (230±30 fs). The calculated product branching ratio (CHD:HT = 64:36) is in agreement with the recent experimental measurement (70:30). The NAMD trajectories are analysed in terms of the vibrational normal modes and the obtained branching ratio is explained by persistent stretching of the fissile bond when the trajectories propagate on the S 1 PES. GRAPHICAL ABSTRACT: