Tutorial on computing nonadiabatic proton-coupled electron transfer rate constants

Area of Science:

• Multidisciplinary science
• Physical chemistry
• Biophysics

Background:

• Proton-coupled electron transfer (PCET) is a fundamental process in chemistry, biology, and physics.
• A general theoretical framework for PCET has been developed, incorporating quantum mechanical effects of electrons and protons, hydrogen tunneling, environmental reorganization, and donor-acceptor fluctuations.
• Analytical rate constants have been derived for various regimes, with a focus on the vibronically nonadiabatic regime.

Purpose of the Study:

• To provide a tutorial on computing input quantities for PCET rate constants in the vibronically nonadiabatic regime.
• To detail the calculation of inner-sphere and outer-sphere reorganization energies, diabatic proton potentials, electronic coupling, reaction free energy, and proton donor-acceptor distance distribution.
• To guide the determination of electron-proton nonadiabaticity for vibronic coupling.

Main Methods:

• Focus on the golden rule rate constant expression applicable to the vibronically nonadiabatic regime.
• Detailed instructions for computing essential input parameters for PCET systems.
• Application of methods to diverse systems including enzymatic, homogeneous molecular electrochemical, photochemical molecular, and heterogeneous electrochemical PCET.

Main Results:

• Provides a comprehensive guide for calculating PCET rate constants.
• Demonstrates the application of the theoretical formulation through detailed examples.
• Introduces the publicly available Python package, pyPCET, for computing nonadiabatic PCET rate constants.

Conclusions:

• The tutorial equips researchers with the necessary tools and knowledge to compute PCET rate constants.
• The pyPCET package facilitates the application of advanced theoretical methods to various PCET systems.
• This work enhances the understanding and computational accessibility of complex PCET processes across scientific disciplines.