Applying electric field to charged and polar particles between metallic plates: Extension of the Ewald method

TL;DR

This paper introduces an extended Ewald method for molecular dynamics simulations to accurately compute electrostatic interactions of charged and polar particles between metallic plates under arbitrary electric fields, accounting for boundary effects.

Contribution

The authors develop a novel Ewald method that incorporates image charges and dipoles for simulations with metallic boundaries and applied electric fields, improving accuracy in boundary effect analysis.

Findings

Boundary effects significantly influence charged and polar fluids.

Large deviations from classical Lorentz-field relation observed in polar fluids.

Formation of ionic crystals and dipole chains depends on applied field and image interactions.

Abstract

We develop an efficient Ewald method of molecular dynamics simulation for calculating the electrostatic interactions among charged and polar particles between parallel metallic plates, where we may apply an electric field with an arbitrary size. We use the fact that the potential from the surface charges is equivalent to the sum of those from image charges and dipoles located outside the cell. We present simulation results on boundary effects of charged and polar fluids, formation of ionic crystals, and formation of dipole chains, where the applied field and the image interaction are crucial. For polar fluids, we find a large deviation of the classical Lorentz-field relation between the local field and the applied field due to pair correlations along the applied field. As general aspects, we clarify the difference between the potential-fixed and the charge-fixed boundary conditions and examine the relationship between the discrete particle description and the continuum electrostatics.