The modified Redfield equation (MRE) is a generalization of Fermi’s golden rule (FGR), in the sense that it accounts for the dynamics of the entire electronic density operator, as opposed to just the electronic populations, and can accommodate nonequilibrium nuclear dynamics, non-Markovian and non-secular effects. Thus, the MRE provides a rigorously derived exact description of the nonadiabatic dynamics of the electronic reduced density operator, as long as the coupling between the electronic states can be treated at the level of second order perturbation theory. Within the MRE, the effect of the nuclear degrees of freedom on the electronic degrees of freedom can be captured by a memory kernel matrix. Calculating this memory kernel matrix within the framework of the linearized semiclassical (LSC) approximation, then makes it feasible to apply the MRE to anharmonic systems with arbitrary potential energy surfaces. The accuracy of the LSC-based MRE is tested on a set of benchmark models by comparing it to quantum-mechanically exact results obtained via ML-MCTDH. The method is found to be accurate over a wide range of parameter space and the importance of accounting for non-Markovian effects, even in the weak coupling limit, is demonstrated.

Using the linearized semiclassical approximation to simulate nonadiabatic dynamics of complex molecular systems via the modified Redfield equation

2019 Spring National Meeting

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