A mapping approach to surface hopping

Fewest-switches surface hopping (FSSH) coupled with first-principles electronic structure theory is a popular approach for simulating ultrafast processes in photochemical systems [1, 2]. However, FSSH is known to suffer from a so-called ‘inconsistency error’ that often significantly degrades the accuracy of its results and requires the application of ad-hoc decoherence corrections to alleviate it. As a result, FSSH is known to incorrectly describe the coherent dynamics induced by an explicit laser pulse [3] and gives order of magnitude errors when calculating Marcus theory rates [4]. This in part has motivated the development of more expensive coupled-trajectory Gaussian wavepacket approaches, such as ab-initio multiple spawning (AIMS) [5], in order to try and achieve a more accurate description of nonadiabatic effects.

In this presentation, I will introduce a mapping approach to surface hopping (MASH) [6], which is a newly developed independent-trajectory surface-hopping approach. I will demonstrate that MASH provides accurate surface-hopping dynamics without the need for decoherence corrections, therefore allowing the accurate simulation of strong laser-driven processes and Marcus theory rates [7] at a comparable computational cost to FSSH. Through application to ab-initio simulations of molecules, I will show that MASH can even provide more accurate dynamics than AIMS at a fraction of the cost [8].

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[5] B. F. E. Curchod, T. J. Mart´ınez, Chem. Rev. 2018, 118, 3305–3336.
[6] J. R. Mannouch, J. O. Richardson, J. Chem. Phys. 2023, 158, 104111.
[7] J. E. Lawrence, J. R. Mannouch, J. O. Richardson, J. Phys. Chem. Lett. 2024, 15, 707–716.
[8] J. R. Mannouch, A. Kelly, J. Phys. Chem. Lett. 2024, 15, 5814–5823.