Robustness of attosecond molecular modes under nuclear dynamics

We investigate the impact of nuclear motion on attosecond charge migration modes, characterized by low-frequency and long-distance hole density patterns in polyatomic molecules. We create the initial hole density using constrained density functional theory and track the subsequent electron-ion dynamics using the Ehrenfest dynamics together with the time-dependent density functional theory. Our focus is on a prototypical ${\mathrm{BrC}}_{4}\mathrm{H}$ system, where we examine the effects of alterations in initial nuclear geometry. We find that the nuclear motion drives and transforms the charge migration modes, underscoring the strong connection between hole patterns and nuclear dynamics. For various initial stretches or bends, these modes demonstrate considerable robustness to the nuclear motion, i.e., they do not dissipate under the classical nuclear motion throughout the computational time. We discover that the charge migration modes correspond to prominent peaks in the frequency spectra of the electronic dipole moment. Additionally, our calculations indicate that the modes primarily originate from the last four atoms near the halogen site and are predominantly attributed to the hole density closest to these nuclear trajectories. Our study offers insights into the behavior of the charge migration modes under varying nuclear geometry and may have implications for understanding related nuclear effects.