To understand these drastic drops in EET efficiency for smaller interparticle spacings, we need an intuitive way to analyze these excitations. Fig. shows the charge distributions and the time-dependent changes in Mulliken charges for the NP dimer with an interparticle spacing of 1 Å. In the panels of this figure, we compare the time-dependent dynamics when the NP dimer is excited at either the BDP or CTP energy peak. When the NP dimer is excited at the CTP peak, one of the NPs shows a predominantly positive charge, while the other one shows a negative charge (Fig. (a)). The time-dependent changes in Mulliken charges confirm this observation in Fig. ). This behavior is characteristic of a CTP excitation, where an oscillating current occurs between the two NPs of the dimer. Also note in Fig. (a) that we observe a slight dipolar nature of charge distributions near the particle edges. This can be attributed to the atomistic treatment of the nanoparticles, whereby the charge transfer plasmon induced on the nanoparticle dimers also establishes a small opposing dipole on the inner edges of the same nanoparticles due to inter-atomic electrodynamic interactions. However, when the NP is excited at the BDP peak, we observe some charge transfer from one NP to the other, which is uncharacteristic of a BDP excitation. In particular, we observe that at subnanometer interparticle spacings, the pure BDP excitation forms a hybridized excitation that has some CTP character. As such, the decrease in the EET efficiency in smaller interparticle spacing chains can be attributed to the formation of this hybridized BDP. Because the hybridized BDP allows for a small charge transfer between the NPs, it reduces the capacitive coupling between the NPs. Going back to the capacitor analogy used previously, this can be thought of as a leaking capacitor. This, in turn, is ultimately responsible for the reduction in capacitive coupling between the NPs and hence the drop in EET efficiency, as revealed by these RT-TDDFTB calculations. Until now, we have highlighted the use of RT-TDDFTB to probe the electron dynamics of large systems in external electric fields where the nuclei are held fixed. However, in this section, we discuss and give examples where this constraint is relaxed, and the nuclei are allowed to evolve nonadiabatically on different potential surfaces. We first give a general overview of nonadiabatic dynamics and present a specific example of how DFTB can be further extended to give mechanistic insight in these excited-state processes.