Time-Domain Atomistic Theory and Simulation of Excitation Dynamics on the Nanoscale

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Oleg V. Prezhdo of the University of Southern California is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop computational approaches to study nanoscale materials. The award is cofunded by the Condensed Matter and Materials Theory program in the Division of Materials Research. Studying matter at the nanoscale allows scientists and engineers to develop smaller and faster electronic and electro-optic devices. These devices have many technological benefits. For example, they can improve the efficiency and lower the cost of solar cells. Many new technologies, such as those relevant to quantum information science also emerge from nanoscale research. Bridging the gap between molecular and bulk scales, nanoscale materials exhibit novel phenomena. An atom-level description and fine time-resolution are needed to understand these phenomena. To gain this detailed understanding, Professor Prezhdo and his research group develop novel theoretical methods and use them to study ultrafast dynamics in nanomaterials. This theoretical research is performed in close collaboration with experimentalists. The current focus of the Prezhdo group is on hybrid organic/inorganic perovskites, which show record solar cell efficiencies, as well as on two-dimensional materials, such as metal dichalcogenides and black phosphorus, which can lead to the development of devices that are just a few atoms in thickness. Professor Prezhdo is engaged at curriculum development aimed at increasing student involvement in energy sciences.These studies are rooted in the recent advances in nonadiabatic (NA) and semi-classical molecular dynamics (MD), and their implementation within time-domain density functional theory (TDDFT). The focus is on the investigation of the fundamental questions posed in the recent time resolved experiments performed on nanoscale materials. Specific attention is given to the development and testing of new simulation approaches and algorithms for NAMD with focus on rigor, accuracy, efficiency and applicability to large systems, which undergo practically important non-equilibrium processes involving excited electronic states and ultrafast timescales. The implementation and testing of the NAMD approaches within TDDFT with the goal of extending the applicability of NAMD to new problems and larger systems is also a goal of this research. The larger systems have electronic structure can be described by ab initio and tight binding DFT, including a new family of NAMD techniques (Liouville space NAMD) and types of processes (many-particle and spin-orbit interactions). Finally, the study of the excitation dynamics in two-dimensional materials and halide perovskites, which are under intense experimental investigation are investigated. These materials carry great promise for photovoltaic, photocatalytic, electronic, spintronic, plasmonic, valleytronic and related technologies, underlying future societal advances in energy harvesting and information processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.