Deriving effective electrode-ion interactions from free-energy profiles at electrochemical interfaces

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Materials Science

Background:

• Accurate modeling of electrochemical systems necessitates understanding ion adsorption at electrified metal-electrolyte interfaces.
• Classical force fields often struggle with accurate ion-metal interactions due to parameterization challenges.

Purpose of the Study:

• To systematically investigate ion adsorption free energy profiles at the Au(111)-water interface.
• To evaluate the performance of classical force fields and machine-learned interatomic potentials (MLIPs) for describing ion adsorption.
• To integrate molecular-level adsorption data into continuum models of the electric double layer.

Main Methods:

• Enhanced sampling molecular dynamics simulations.
• Classical metadynamics using Lennard-Jones potentials.
• Machine-learned interatomic potentials (MLIPs), specifically the Universal Models for Atoms.
• Integration of molecular adsorption energies into continuum electric double layer models.

Main Results:

• Classical force field predictions are highly sensitive to Lennard-Jones parameters; standard mixing rules can yield incorrect ion adsorption energetics.
• MLIPs validate classical trends and predict specific adsorption for chloride, weak adsorption for fluoride, and no specific adsorption for sodium.
• Incorporating molecular adsorption free energies into continuum models significantly alters interfacial ion populations, potential of zero charge, and differential capacitance.

Conclusions:

• Precise force field parameterization and advanced interatomic potentials like MLIPs are crucial for predictive modeling of ion-specific effects at electrified interfaces.
• A robust framework is provided for bridging molecular simulations and continuum electrochemical models.
• This work emphasizes the importance of accounting for specific ion adsorption in electrochemical modeling.