Mathematical and Computational Methods in Quantum Chemistry

Nonadiabatic Molecular Dynamics with Time-Domain Density Functional Theory

Oleg Prezhdo

University of Southern California


Modeling of non-equilibrium excited state processes in nanoscale systems create new challenges to time-domain density functional theory (TDDFT) and nonadiabatic molecular dynamics (NAMD). Examples include proper treatment of quantum coherence, transition from coherent to hopping transport in long-range charge and energy transfer, super-exchange, and many-particle Auger-type processes. Motivated by these challenges, our group developed several new NAMD techniques and implemented them within TDDFT. Decoherence-induced surface hopping (DISH) incorporates decoherence effects in a way that naturally achieves trajectory branching. Coherence penalty functional (CPF) uses DFT-like ideas to introduce decoherence into the Ehrenfest method. Self-consistent fewest-switches surface hopping (SC-FSSH) provides a simple solution to the trivial (or “unavoided”) crossings in FSSH. Global flux surface hopping (GFSH) generalizes FSSH to treat super-exchange. Second quantized surface hopping (SQUASH) utilizes second quantization and generalizes FSSH to include both super-exchange and decoherence effects. Liouville space formulations of FSSH and related techniques treats populations and coherences on equal footing, while maintaining low computational cost. We will introduce the key ideas underlying these NAMD-TDDFT approaches, and illustrate their utility with applications to excited state dynamics in nanoscale materials.