Multicomponent Time-Dependent Density Functional Theory: Proton and Electron Excitation Energies

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• Accurate calculation of excited state properties requires quantum mechanical treatment of electrons and protons.
• Nonadiabatic processes like proton-coupled electron transfer are vital in chemical reactions.
• Existing methods often treat nuclei and electrons separately, limiting accuracy for certain phenomena.

Purpose of the Study:

• To derive and implement linear response multicomponent time-dependent density functional theory (NEO-TDDFT).
• To enable accurate quantum mechanical treatment of both electrons and protons for excited state properties.
• To provide a computational tool for studying nonadiabatic processes.

Main Methods:

• Development of linear response multicomponent time-dependent density functional theory (TDDFT).
• Implementation within the nuclear-electronic orbital (NEO) framework.
• Application to model systems like FHF- and HCN.

Main Results:

• NEO-TDDFT accurately calculates proton and electron excitation energies in a single computation.
• The computational cost is comparable to conventional electronic TDDFT.
• Demonstrated accuracy for FHF- and HCN systems.

Conclusions:

• NEO-TDDFT is a promising method for studying excited state properties involving both electrons and protons.
• The approach is particularly valuable for nonadiabatic proton transfer reactions.
• It opens avenues for exploring mixed electron-proton vibronic excitations.