Effect of the surface charge discretization on electric double layers: a Monte Carlo simulation study

Area of Science:

• Physical Chemistry
• Computational Physics
• Surface Science

Background:

• Understanding the electric double layer (EDL) is fundamental in colloid science, electrochemistry, and interfacial phenomena.
• Previous models often simplified charged surfaces as continuous, potentially overlooking discreteness effects.
• The primitive model provides a foundational framework for simulating ionic solutions near charged interfaces.

Purpose of the Study:

• To investigate the structural impact of discrete versus continuous charge distributions on planar surfaces within the EDL.
• To analyze charge density profiles and their dependence on surface charge discretization.
• To compare simulation results with uniform charge distribution models and highlight discrepancies.

Main Methods:

• Utilized Monte Carlo simulations within the primitive model framework.
• Employed three distinct discretization models for surface charges.
• Included a comparative analysis with a uniformly distributed charge model.

Main Results:

• Point surface charges showed equivalence to uniform charge distributions when analyzing profiles solely by distance from the surface.
• Deviations in charge density profiles were observed when moving parallel to discrete surfaces.
• Significant discrepancies arose when considering finite-sized surface charge sites, differing from non-discretized models.

Conclusions:

• Surface charge discreteness significantly influences electric double layer structure.
• The assumption of uniform charge distribution can be inadequate, particularly for finite-sized surface elements.
• Accurate modeling of EDLs requires consideration of surface charge heterogeneity.