Concerted Swing-Coupled Double Proton Tunneling Induced by Dispersion Interaction: Quantum Dynamics for the Formic...

Area of Science:

• Quantum Chemistry
• Chemical Dynamics
• Molecular Interactions

Background:

• Proton (hydrogen atom) transfer via tunneling is crucial in chemical and biological processes.
• Understanding multiple or concerted proton tunneling remains a challenge.

Purpose of the Study:

• Investigate the impact of weak dispersion interactions on double proton transfer (DPT) in the formic acid dimer (FAD)-fluorobenzene (PhF) system.
• Characterize the coupled dynamics of DPT and FAD swing.

Main Methods:

• Reduced-dimensionality quantum dynamics calculations.
• Development of an efficient calculation scheme.
• Construction of a highly accurate 30-dimensional *ab initio* neural network potential energy surface.

Main Results:

• Weak dispersion interaction does not alter the DPT barrier in FAD but induces a coupled FAD swing.
• A triple concerted phenomenon involving DPT and FAD swing was identified.
• The concerted swing-coupled DPT reduces the tunneling rate.
• Calculated tunneling splittings show excellent agreement with experimental data.

Conclusions:

• The study provides a deeper understanding of nuclear quantum effects.
• Concerted swing-coupled DPT in FAD-PhF systems could be applicable in quantum science, such as molecular clocks or qubits.