Ions at electrochemical interfaces: From explicit to implicit molecular solvent descriptions.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Understanding interfacial phenomena is crucial for electrochemical systems.
• Electronic screening in metals and solvent screening are key factors at interfaces.
• Accurate modeling of these interactions is computationally challenging.

Purpose of the Study:

• To investigate the combined effects of electronic and solvent screening on ion-induced charge.
• To analyze the influence of screening on interfacial solvent structure.
• To evaluate molecular density functional theory (MDFT) against molecular dynamics (MD) for modeling these systems.

Main Methods:

• Atomistically resolved electrodes using the Thomas-Fermi model for metal screening.
• Classical molecular dynamics (MD) for explicit solvent description.
• Molecular density functional theory (MDFT) for implicit solvent description.
• Varying Thomas-Fermi screening length (lTF), ion charge (Na+, Cl-), and solvent type (water, acetonitrile).

Main Results:

• The Thomas-Fermi screening length (lTF) significantly alters charge distribution within the metal.
• lTF shows no significant impact on the interfacial solvent structure.
• The metal's response to the external charge distribution, including the solvent, is the primary driver of internal charge changes.
• MDFT accurately captures interfacial solvent structure details with lower computational cost than MD.

Conclusions:

• The interplay between metal and solvent screening has distinct effects on metal charge distribution and interfacial structure.
• MDFT is a computationally efficient and accurate method for modeling molecular-level details in electrochemical interfaces.
• This work provides insights into the fundamental mechanisms governing charge distribution and solvation at electrified interfaces.