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QM/MM Nonadiabatic Decay Dynamics of 9 H ‐Adenine in Aqueous Solution
Author(s) -
Lan Zhenggang,
Lu You,
Fabiano Eduardo,
Thiel Walter
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201001054
Subject(s) - photoexcitation , chemistry , qm/mm , surface hopping , vibronic coupling , conical intersection , molecular dynamics , excited state , aqueous solution , solvation , spectroscopy , potential energy , internal conversion , potential energy surface , singlet state , molecular physics , atomic physics , quantum yield , computational chemistry , solvent , physics , molecule , spectral line , quantum mechanics , fluorescence , organic chemistry
The photoinduced nonadiabatic decay dynamics of 9 H ‐adenine (hereafter, adenine) in aqueous solution were investigated by surface‐hopping simulations within a quantum mechanical/molecular mechanical (QM/MM) framework. The QM subsystem (adenine) was treated at the semiempirical OM2/MRCI level, whereas the MM solvent (water) was described by the TIP3P force field model. Classical molecular dynamics (MD) simulations were used to generate snapshots with different solvent configurations and geometries. For a representative number of these snapshots, the energy minima of the lowest electronic states and the most important conical intersections were located by QM/MM geometry optimization. Surface‐hopping QM/MM MD simulations were performed for all selected snapshots to study the nonadiabatic dynamics after photoexcitation, including the two lowest excited singlet states, which are both populated in the initial photoexcitation due to strong vibronic coupling in the Franck–Condon region. The simulations yield ultrafast S 2 –S 1 decay within 40 fs and S 1 –S 0 internal conversion to the ground state within 410 fs, which is consistent with recent experimental results from time‐resolved spectroscopy.