In this final section on RT-TDDFTB dynamics, we give an example of the techniques used in the previous tutorial section on a "real-life" application to a large system. In particular, we focus on the real-time electron dynamics of excitation energy transfer (EET) in a large plasmonic nanoantenna system using the RT-TDDFTB formalism. Understanding and achieving a controlled transfer of energy in these novel systems has been a continual area of interest in various technologies including nanophotonic circuits, waveguide materials, and other natural light-harvesting antenna systems. Absorption Spectrum of a Single Plasmonic Nanoparticle We begin our analysis of EET by first characterizing the plasmon resonance energy of a single nanoparticle (NP) containing 55 silver atoms and having an icosahedral shape. The geometry of this NP was optimized with the DFTB+ package using the hyb-0-2 set of DFTB parameters (available at dftb.org), and its absorption spectrum was obtained in the same manner as described in the tutorial section on naphthalene. As can be seen in Fig. , a prominent peak, corresponding to the plasmon resonance is observed around 3.23 eV. This result is in good agreement with a time-dependent density functional theory (DFT) calculation of 3.6 eV 44 and a recent experimental result of 3.8 eV for similar-sized Ag nanoparticles.