Physics and Astronomy Colloquium - Dr. Sharon Hammes-Schiffer

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"Nuclear-Electronic Orbital Theory: Exploring Nuclear Quantum Effects in Chemistry and Materials"

Presented by Sharon Hammes-Schiffer, A. Barton Hepburn Professor of Chemistry from Princeton University.

The nuclear-electronic orbital (NEO) approach directly incorporates nuclear quantum effects and non-Born-Oppenheimer effects into quantum chemistry calculations and molecular dynamics simulations. This approach treats specified nuclei, typically protons, quantum mechanically on the same level as the electrons with multicomponent density functional theory (DFT) or wavefunction methods, such as coupled-cluster and multireference approaches. Nuclear delocalization and anharmonic zero-point energy are inherently included in energy calculations, geometry optimizations, reaction paths, and dynamics. The NEO approach also provides accurate descriptions of excited electronic, vibrational, and vibronic states, as well as nuclear tunneling and nonadiabatic dynamics. The real-time NEO methods enable nonequilibrium nuclear-electronic quantum dynamics simulations beyond the Born-Oppenheimer approximation for investigating thermal and photoexcited chemical reactions. NEO calculations can be performed in implicit or explicit solvent, proteins, or periodic solids. This talk will present foundational and recently developed NEO methods as well as a wide range of applications. The applications will include water clusters, proton-coupled electron transfer, hydrogen tunneling dynamics, photoinduced proton transfer, pKa and kinetic isotope effect calculations, enzymatic reactions, geometric isotope effects, hydrogen and deuterium adsorption and water monolayers at metal electrode surfaces, phase transitions in hydrogen-rich materials such as superconducting hydrides and ice, and polaritonic and plasmonic chemistry. These examples showcase the ubiquitous importance of nuclear quantum effects.