Including diverging electrostatic potential in 3D-RISM theory: The charged wall case

Area of Science:

• Theoretical Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Standard 3D-Reference Interaction Site Model (3D-RISM) struggles with divergent electrostatic potentials at solid-liquid interfaces.
• Macroscopic substrates with charged planes create potentials incompatible with Fourier transformable functions required by 3D-RISM.

Purpose of the Study:

• To develop a computational scheme for characterizing electrical double layers at solid-liquid interfaces.
• To overcome limitations of existing theoretical models in handling divergent electrostatic potentials.
• To accurately calculate the 3D electrostatic potential profile at the interface.

Main Methods:

• Application of a renormalization procedure to address divergent electrostatic potentials.
• Utilizing the electrostatic potential of an infinite wall, periodic in 2D, to avoid edge effects.
• Robust integration of Poisson's equation for 3D potential profile calculation.
• Testing the method on a gold (111) surface with water/alkali chloride solution.

Main Results:

• The renormalization procedure successfully overcomes limitations of standard 3D-RISM for interface calculations.
• The method achieves converged charge densities with high spatial resolution, proving computationally efficient.
• The 3D electrostatic potential profile reveals oscillations not predicted by Debye-Hückel or Gouy-Chapman theories.
• Deviations of 1-2 V from the average potential were observed near the substrate.

Conclusions:

• The developed computational scheme accurately models electrical double layers at solid-liquid interfaces.
• The findings challenge existing theories by demonstrating significant potential oscillations.
• This advancement has potential applications in techniques like liquid scanning tunneling microscopy.