Molecular dynamics (MD) calculation of the zeta potential of neutral surfaces

TL;DR

This paper presents an improved molecular dynamics simulation method for accurately calculating the zeta potential of neutral surfaces, aligning closely with experimental measurements by integrating charge distributions and modeling slip planes.

Contribution

It introduces a novel approach combining charge integration, slip plane determination, and static potential calculations to enhance MD prediction accuracy for zeta potentials.

Findings

Calculated zeta potentials match measured values within error margins.

The method provides insights into surface charge phenomena affecting zeta potential.

Improved simulations clarify the influence of surface and ion properties on electrostatic behavior.

Abstract

Molecular dynamics (MD) simulations of the zeta potential are so poor that it has become common to term their predictions 'apparent'. Here we demonstrate how zeta potentials that agree with measured values can be calculated by: (1) integrating the net average charge in surface-parallel layers from the midpoint of the fluid layer (where the electrostatic potential is zero) to and then into two solid caps, (2) determining the position of slipping plane with separate Couette flow models, and (3) calculating the charge distribution and electrostatic potential under static conditions. The solids we model are charge neutral surfaces composed of atoms with zero charge or charge balanced monovalent or divalent ions. The zeta potentials calculated are within a few millivolts of measured values, and the measured values fall within the simulation error bars. Insights provided by the improved MD simulations into the complex phenomena that affect surface charge and zeta potential are discussed.