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Updated: Mar 31, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
An Ab Initio QM/MM-Based Approach to Efficiently Evaluate Vertical Excitation Energies in Condensed Phases Including
Hiroshi Nakano1,2, Hirofumi Sato1,2
1Department of Molecular Engineering, Kyoto University , Kyoto 615-8510, Japan.
Abstract:
An efficient quantum mechanical/molecular mechanics-based approach is presented to calculate a vertical excitation energy of a chromophore in condensed phases including the nonequilibrium solvation effect. The electronic polarization of a medium and the related nonequilibrium solvation effect associated with the vertical excitation are described using a polarizable solvent model. By virtue of the mean-field approximation, the target energy can be completely separated into classical and quantum mechanical parts, which enables us to efficiently evaluate the vertical excitation energy with a high-level quantum mechanical method. The method is applied to N,N-dimethyl-4-nitroaniline in a variety of solutions at the MRMP2/CASSCF level, showing quantitative agreement with the experimental reports. The observed large bathochromic shifts are analyzed by focusing on the induction effects of the solvents.
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