Ultrafast Reactive Quantum Dynamics Coupled to Classical Solvent Dynamics Using an Ehrenfest Approach

Abstract

The inclusion of solvent effects in the theoretical analysis of molecular processes becomes increasingly important. Currently, it is not feasible to directly include the solvent on the quantum level. We use an Ehrenfest approach to study the coupled time evolution of quantum dynamically treated solutes and classical solvents system. The classical dynamics of the solvent is coupled to the wavepacket dynamics of the solute and rotational and translational degrees of freedom of the solute are included classically. This allows quantum dynamics simulations for ultrafast processes that are decided by environment interactions without explicit separation of time scales. We show the application to the dissociation of ICN in liquid Ar as a proof of principal system and to the more applied example of uracil in water.

Theoretical Quantum Control of Fluctuating Molecular Energy Levels in Complex Chemical Environments

“…Other solvent effects which are not included in the theoretical framework, like the energy transfer from the solute back to the solvent are shown to be minor in the present control window. In the future, coupled approaches could be used to investigate the controllability of these effects simultaneously.…”

“…In contrast to another explicit scheme, where random snapshots along a MD trajectory are used to parametrize the environmental influence within a fluctuating Hamiltonian, here the molecular reactant is considered within its individual and mobile microscopic environment. The remaining approximation, in contrast to recent theoretical advances which simultaneously propagate QD and MD domains, is that the influence of the quantum system dynamics on the solvent environment is not included. With respect to Equation , this means that the off‐diagonal elements in the energy level matrix are zero and there is no population transfer if the laser field is switched off.…”

Quantum and semiclassical dynamical studies of nonadiabatic processes in solution: achievements and perspectives

“…A possible strategy to describe approximately the coupling between the quantum and classical DoFs is provided by a mean-field/Ehrenfest approach, in which classical DoFs feel the average potential exerted from the quantum density, while the QD includes solvent coordinates as TD parameters. 117,212 In ref. 117 Spp* -Snp* decay for thymine in water was investigated, performing QD simulations of the coupled diabatic states described with a LVC model, and adopting ML-MCTDH to propagate a wavepacket along all solute coordinates on the coupled PESs, while water molecules move classically.…”

“…136 A similar MQC approach is adopted in ref. 212 where the S 2 -S 1 decay of uracil in water is simulated. A reduced dimensionality (2D) representation of the solute is adopted, in keeping with previous investigations of the effect of static disorder, 211 using a similar strategy to account for the effect of the explicit solvent coordinate on this 2D-PES.…”

“…4 and compared with those obtained with a system-bath approach. are based on MQC partitions, 117,[210][211][212] where only a reduced number of nuclear degrees of freedom (DoFs) are propagated with QD, while the remaining ones evolve in time according to classical MD. As mentioned previously, here the MQC partition is based on the different treatment of nuclear dynamics, and usually the solute is included in the quantum region and the solvent in the classical one.…”