Computing Hydrogen Tunneling Splittings with Nuclear-Electronic Orbital Multireference Configuration Interaction

2025/06/02 by Stein, Rachel J., Christopher L. Malbon, Sharon Hammes‐Schiffer +2 · 2 citations
Physics and Astronomy · #Advanced Chemical Physics Studies #Chemical Physics (physics.chem-ph) #FOS: Physical sciences

paper · pdf · doi:10.48550/arxiv.2506.02201

openalex publication_date 2025/06/02 · openalex created_date 2025/10/14 · openalex updated_date 2026/07/28

Abstract

Hydrogen tunneling is an important process that impacts reaction rates and molecular spectra. Describing and understanding this process requires a quantum mechanical treatment of the transferring hydrogen. The nuclear-electronic orbital (NEO) approach treats specified nuclei quantum mechanically on the same level as electrons and has recently been implemented at the multireference configuration interaction (MRCI) wavefunction level. The NEO-MRCI method includes both the static correlation necessary to describe hydrogen tunneling and the electron-proton dynamic correlation required for computing quantitatively accurate nuclear-electronic vibronic states. Herein, the NEO-MRCI method is used to compute the nuclear-electronic wavefunctions and corresponding vibronic energies for four hydrogen tunneling systems at fixed geometries for a range of donor-acceptor distances. Comparison of the NEO-MRCI results to numerically exact grid-based calculations shows that the NEO-MRCI method can be used to obtain accurate hydrogen and deuterium tunneling splittings at fixed geometries. Thus, this work presents an important component for studying hydrogen tunneling systems.

Citations

• Nuclear-Electronic Orbital Multireference Configuration Interaction for Ground and Excited Vibronic States and Fundamental Insights into Multicomponent Basis Sets
• Multicomponent CASSCF Revisited: Large Active Spaces are Needed for Qualitatively Accurate Protonic Densities
• Tunneling-splittings from path-integral molecular dynamics using a Langevin thermostat

Cited by

• Nuclear-electronic orbital second-order coupled cluster for excited states
• Simulation of Vibronic Strong Coupling and Cavity-Modified Hydrogen Tunneling Dynamics

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