Real-time path integral methodology for condensed-phase quantum dynamics

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Nancy Makri of the University of Illinois is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop accurate computational methods for studying proton, electron, and energy transfer processes in chemical and biological systems. These transfer processes play a vital role in living organisms, as well as in energy production and storage. Reactions involving light particles and energy transfer are dominated by quantum mechanical effects. These effects are based on the idea that elementary particles (protons, electrons, etc.) also behave as waves and thus, have mathematical interpretations of their structure and interactions with other matter. Quantum mechanical effects cannot be modeled correctly using classical treatments. Professor Makri and her coworkers design new theoretical and computational approaches for circumventing this problem; their approaches produce more accurate and efficient simulation algorithms. The resulting software may aid in the interpretation of experimental results. The new software enhances the learning experience in the classroom by augmenting the visualization ability offered by classical simulations. The project offers graduate students and a postdoctoral researchers opportunities to receive training in quantum dynamics, mastering state-of-the-art theoretical ideas and simulation tools. The traditional formulation of quantum mechanics is based on wave functions, which require array storage that far exceeds current computer capabilities. Makri’s approach is based on the fully quantum mechanical path integral formulation while the influence of thousands of solvent or protein atoms on the dynamics of the quantum system of interest is captured through classical trajectories. The real-time path integral methods developed by Makri’s group are free of assumptions and uncontrolled approximations, leading to highly accurate results. In the case where the effects of the environment are described in terms of a harmonic bath, Makri’s work may extend the capabilities of simulation algorithms to systems with long memory and multiple states.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.