Benchmarking non-adiabatic quantum dynamics using the molecular Tully models

Abstract

On-the-fly non-adiabatic dynamics methods are becoming more important as tools to characterise the time evolution of a system after absorbing light. These methods, which calculate quantities such as state energies,...

Simulating Attochemistry: Which Dynamics Method to Use?

“…We analyzed the nuclear motion in the branching space of the nearby CI to investigate the charge-directed reactivity. Mixed quantum-classical methods can reproduce quantitatively the quantum nuclear motion induced by pure electronic adiabatic states (or an incoherent superposition of them) as in standard photochemistry, consistently with literature. − In this case, the resulting nuclear motion is mostly along the gradient difference coordinate, in the positive or negative direction, depending on the excited electronic state.…”

“…Recent works have evaluated the effect of the choice of the dynamics methods and algorithms on femtochemistry with initial excitation to a single electronic state with little observed difference (in the absence of quantum nuclear tunneling). − In the context of attochemistry with initial coherent excitation to a superposition of electronic states, mixed quantum-classical methods, like Ehrenfest and TSH, are commonly employed in the literature. − ,− However, the impact of the approximations underlying such dynamics methods on the simulations of attochemical reactions remains unknown. The goal of the present paper is to compare the suitability of several dynamics methods for charge-directed reactivity: DD-vMCG, TSH, and Ehrenfest (see Figure for a schematic representation).…”

Quantum Quality with Classical Cost: Ab Initio Nonadiabatic Dynamics Simulations Using the Mapping Approach to Surface Hopping

“…To complement the above comparison of the various dynamics approaches in the ab initio case, we also performed simulations for linear vibronic coupling (LVC) models fit to the electronic structure data for DMABN and fulvene. These LVC models have already been used to perform numerically exact quantum dynamics using the multiconfiguration time-dependent Hartree (MCTDH) approach, along with some vMCG calculations . Given that it is significantly easier to compute diabatic populations with MCTDH, and adiabatic populations with AIMS, we provide both quantities in Figure .…”

“…Electronic populations of the upper adiabatic state ( false⟨ P̂ + ( t ) false⟩ ) and the diabatic state that coincides with this adiabat at the Franck–Condon geometry ( false⟨ P̂ normald normali normala normalb ( t ) false⟩ ) , obtained for the linear vibronic coupling (LVC) models that were constructed for DMABN and fulvene in ref . The MCTDH and vMCG results were also obtained from ref . We do not consider the analogous LVC model for ethylene, as it was found to not give rise to any electronic population transfer.…”

“…In order to determine a hierarchy in the accuracy of these approaches, we also compare with numerically exact quantum dynamics applied to linear vibronic coupling (LVC) models previously parametrized for these molecules. 7 Before discussing the relaxation dynamics of the three photoexcited molecular systems, we give a brief overview of the dynamics approaches used in this work with a particular emphasis on their similarities and differences. More information can be found in refs 9−12.…”