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Mixed quantum-classical simulations of intramolecular singlet fission
Rudolf Smorka1, Johan E Runeson1, Michael Thoss1
1Institute of Physics, Albert-Ludwigs University Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany.
The Journal of Chemical Physics
|July 17, 2026
Summary
We benchmarked quantum-classical methods for simulating intramolecular singlet fission. The mapping approach to surface hopping (MASH) accurately predicts triplet-pair formation dynamics, offering a robust simulation route.
Area of Science:
- Physical Chemistry
- Quantum Dynamics
- Computational Chemistry
Background:
- Intramolecular singlet fission is a crucial process for efficient solar energy conversion.
- Understanding the ultrafast dynamics of triplet-pair formation is key to optimizing this process.
- Vibronic couplings play a significant role in governing singlet fission dynamics.
Purpose of the Study:
- To benchmark different mixed quantum-classical methods for simulating intramolecular singlet fission.
- To compare the accuracy and reliability of Ehrenfest dynamics, spin-LSC, and MASH against numerically exact methods.
- To analyze the impact of zero-point motion on the accuracy of these simulation approaches.
Main Methods:
- Mixed quantum-classical dynamics simulations: Ehrenfest dynamics, linearized semiclassical spin-mapping (spin-LSC), and mapping approach to surface hopping (MASH).
- Numerically exact multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) calculations.
- Modeling of phenylene-linked pentacene dimers.
Main Results:
- Ehrenfest dynamics shows significant mean-field artifacts and incorrect long-time populations.
- Spin-LSC improves short-time transfer but exhibits unphysical negative populations and back-transfer.
- MASH demonstrates consistent agreement across timescales and molecular variants, avoiding unphysical populations.
- Zero-point motion's influence on initial vibrational distribution affects mapping-based approach accuracy.
Conclusions:
- The mapping approach to surface hopping (MASH) is the most reliable method for simulating intramolecular singlet fission dynamics.
- Spin-mapping surface-hopping methods provide a robust pathway for extending simulations beyond the limits of numerically exact quantum dynamics.
- Accurate simulation of singlet fission is essential for advancing solar energy technologies.
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