Velocity-gauge real-time density functional tight-binding method for large-scale systems

Real-time time-dependent density functional theory in the velocity gauge can probe the electronic excitations of solid-state systems; however, its immense computation cost makes it prohibitive for large systems. In this work, we developed an efficient velocity-gauge real-time method based on density functional tight-binding (VG-rtTDDFTB). We show that the VG-rtTDDFTB absorption spectrum and electron dynamics can generally reproduce the correct spectra for both molecular clusters and periodic systems. Furthermore, we show that the high efficiency of VG-rtTDDFTB allows the simulation of thousands of atoms (only 1 CPU core used), which provides a promising alternative for computing the electronic excitations of large systems.