Linear-response time-dependent density functional theory (LR-TDDFT) is the method of choice for studying singly excited valence electronic states. However, many excited states have a significant contribution from higher order excitations involving multi-electron transitions. Multiconfigurational methods, such as time-dependent configuration interaction (TDCI), accurately capture multi-electron transitions, but become computationally prohibitive for systems larger than a few atoms. A promising alternative is real-time TDDFT (RT-TDDFT). By propagating the electron density in real time and substituting the instantaneous density into ground state density functionals, RT-TDDFT reproduces the absorption spectra predicted by linear response theory when the density remains close to the ground state density. However, it has been shown that RT-TDDFT differs from TDCI in predicting resonant Rabi frequencies. In addition, peak energies of RT-TDDFT spectra shift as the frequency of an applied field is varied. Here, we investigate the origin of this inaccuracy found in RT-TDDFT electron dynamics.

Field-dependent peak shift in real-time time-dependent density functional theory

249th National Meeting (2015)

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