In contrast to the popular linear response matrix formulation of TDDFT, real-time (RT) TDDFT propagates the electron density in the time-domain, including the response of the density to all orders, well beyond the perturbative regime. Because of this time-resolved nonlinear treatment, RT-TDDFT can provide substantially more information about the electron dynamics of the system than the standard linear response approach.  The growing enthusiasm for using RT-TDDFT for simulating electron dynamics in a variety of charge-transfer and photophysical applications indicates that this relatively new methodology needs to be carefully examined, benchmarked, and developed.We will examine the Rabi oscillation behavior of simple molecular systems as the electron density is transferred between the ground and excited states. For two-electron model systems, we will show that the field that induces Rabi oscillation of the population and dipole is not the the linear response frequency. For the simple systems studied herein, the dynamics of this detuning process and 'resonant' field frequency that drives the Rabi oscillation are rationalized in terms of a superposition of population of the ground S0 and doubly-excited S2 states rather than the expected ground S0 and singly-excited S1 states. We will study the electron dynamics behavior as we drive the system away from the ground state density, since this is the regime of interest for RT-TDDFT. Comparisons between the RT-TDDFT charge-transfer and the exact result will be presented.In addition to comparing the RT-TDDFT behavior to exact results on two-electron model systems, we will extend our analysis of the method to the electronic charge-transfer between a donor and acceptor through a conjugated p-system. While RT-TDDFT has been applied to charge-transfer in more complicated systems such as a fullerene derivative of interest in photovoltaics, this density-based method hasn't yet been benchmarked against wavefunction approaches in smaller donor-acceptor molecules.

Electron transfer dynamics with time-domain time-dependent density-functional theory

248th National Meeting (2014)

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