Please join Yale Chemistry for a thesis seminar with Joseph Dickinson, Hammes-Schiffer Group.
Title: Quantum Chemical Methods for Proton Transfer & Hydrogen Tunneling Systems
Summary: Many chemical and biological processes of interest are driven by proton transfer phenomena. A complete picture of proton transfer dynamics requires the incorporation of nuclear quantum effects (NQEs), such as nuclear delocalization, zero-point energy, and tunneling, within its description. Multicomponent quantum chemistry methods, such as the nuclear-electronic orbital (NEO) approach, quantize both electrons and select nuclei within quantum chemical calculations. Such methods result in the natural inclusion of the NQEs associated with the quantized nuclei in the resulting nuclear-electronic structure. Herein, methods within the NEO density functional theory (NEO-DFT) framework are introduced for the description of proton transfer and hydrogen tunneling processes. In particular, an extended Lagrangian approach is formulated for adiabatic dynamics on NEO-DFT vibronic ground states that is shown to approximate exact NEO Born-Oppenheimer molecular dynamics at a dramatically reduced cost. Additionally, a generalized form of the NEO multistate DFT (NEO-MSDFT) method is presented to capture correlated hydrogen tunneling in systems with multiple tunneling hydrogens while accounting for nonadiabatic effects between tunneling-split vibronic states. Finally, a constrained form of adiabatic NEO-MSDFT dynamics is used to sample seam spaces between diabatic NEO-DFT vibronic surfaces, elucidating the vibrational motions that gate hydrogen tunneling in complex asymmetric systems and impact observed rates of proton transfer. The methods introduced herein have wide implications for the simulation of chemical processes where NQEs, especially those associated with transferring or tunneling hydrogens, may have an impact.
