Ab Initio Quantum Dynamics in Nanoscale Materials

Excited state dynamics play key roles in numerous condensed phase and molecular materials designed for solar energy, opto-electronics, spintronics and other applications. Controlling these far-from-equilibrium processes and steering them in desired directions require understanding of material’s response on the nanometer scale and with fine time resolution. We couple, in a unique way, real-time time-dependent density functional theory for the evolution of electrons with non-adiabatic molecular dynamics for atomic motions to model such non-equilibrium response in the time-domain and at the atomistic level. The talk will describe the basics of the simulation methodology and will discuss several recent applications, such as metal halide perovskites, metallic and semiconducting quantum dots, and transition metal dichalcogenides, among the broad variety of systems studied in our group. Interplay of photo-induced charge and energy transfer, Auger-type processes, charge trapping and recombination, and energy losses creates many challenges due to large differences between molecular and periodic, and organic and inorganic matter. Our simulations provide a unifying description of quantum dynamics on the nanoscale, characterize the timescales and branching ratios of competing processes, resolve debated issues, and generate theoretical guidelines for development of novel systems.