MASH
The nonadiabatic dynamics of photoexcited molecules is of fundamental interest because of its impact on biological processes (e.g. vision and photosynthesis) and chemical synthesis. Understanding and predicting these excited-state dynamics is one of the central challenges in modern theoretical chemistry.
It is well established that classical molecular dynamics is sufficient
to simulate the motion of the nuclei, while quantum-mechanical methods
are necessary to describe the electrons. Quantum--classical methods
attempt to combine these two very different pictures in order to couple
the classical motion of the nuclei with the quantum-mechanical
electrons.
Our group has developed a new framework for quantum--classical dynamics, called the mapping approach to surface hopping (MASH). Unlike previously proposed surface-hopping methods, MASH is deterministic and reversible (like Schrödinger's equation) and can be rigorously derived from quantum mechanics in the short-time limit. MASH simulations have already shown improvements in evaluating thermal rates and predicting time-resolved electronic coherence spectroscopies compared to related methods.
It can be applied to study photochemistry using ab initio simulations [https://doi.org/10.1063/5.0203667].
Looking ahead, MASH is open to new developments in transition-path sampling, improved decoherence corrections, simulations of open quantum systems, and incorporating nuclear quantum effects.