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Quantum-Classical Path Integral Simulation of Proton Translocation

Nancy Makri, University of Illinois at Urbana-Champaign

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Nancy Makri, Marco Nava

Combining the quantum mechanics of a small system consisting of discrete quantum states with a classical description of a polyatomic environment poses fundamental difficulties, owing to the incompatibility of nonlocal wavefunctions with local Newtonian trajectories. The quantum-classical path integral (QCPI) methodology removes this incompatibility, providing a rigorous and powerful computational tool for simulating the time evolution of quantum mechanical processes in condensed phase or biological environments. The QCPI formulation is free of approximations besides the classical trajectory description of the nuclei, thus able to capture the delicate interaction of a quantum system with its environment correctly and at full atomistic complexity. It has already been used on Blue Waters with excellent, practically linear scaling, and has been applied to simulate a charge transfer reaction in solution with unprecedented accuracy, while recent advances continue to increase the efficiency of the algorithm. We seek to apply the QCPI methodology to the dynamics of proton translocation in biological channels.