Accelerated constant-voltage quantum mechanical/molecular mechanical method for molecular systems at electrochemical...

Area of Science:

• Computational Chemistry
• Electrochemistry
• Materials Science

Background:

• Molecular structure and electronic properties change at electrochemical interfaces due to surface interactions and applied voltage.
• Simulating these interfaces requires methods that account for both quantum mechanical and molecular mechanical effects.

Purpose of the Study:

• To present an efficient self-consistent quantum mechanics/molecular mechanics (QM/MM) approach for studying molecules at metal electrode-electrolyte interfaces under constant voltage.
• To enable accurate modeling of molecular behavior and electronic properties at electrified interfaces.

Main Methods:

• Developed a QM/MM approach using a classical polarizable double electrode model for constant-voltage simulations.
• Introduced a mean-field embedding approximation to simplify electrolyte configuration sampling.
• Applied the method to a test system of a physisorbed molecule.

Main Results:

• The adsorbed molecule showed significant polarization at the interface, comparable to or greater than in bulk solution.
• Molecular geometry was influenced by electrostatic interactions with the electrode and electrolyte cations during reduction.
• Successfully evaluated the reorganization energy for a one-electron reduction reaction.

Conclusions:

• The developed QM/MM approach is effective for studying molecular behavior at electrified interfaces under applied voltage.
• The method provides quantitative insights into interfacial electronic structure, molecular geometry, and reaction energetics.
• This work advances the computational study of electrochemical systems and molecular electronics.