Counterions and water molecules in charged silicon nanochannels: the influence of surface charge discreteness

TL;DR

This study uses molecular dynamics simulations to explore how surface charge discreteness affects ion and water behavior at charged silicon nanochannels, revealing increased counterion attraction, charge inversion, and limited water distribution impact.

Contribution

It introduces a simulation model considering wall atom vibrations to analyze the effects of surface charge discreteness on interfacial ion and water properties.

Findings

More counterions are attracted with increased charge discreteness.

Charge inversion occurs due to denser ion layers near the surface.

Water distribution is minimally affected by surface charge discreteness.

Abstract

In order to detect the effect of the surface charge discreteness on the properties at the solid-liquid interface, molecular dynamics simulation model taking consideration of the vibration of wall atoms was used to investigate the ion and water performance under different charge distributions. Through the comparison between simulation results and the theoretical prediction, it was found that, with the degree of discreteness increasing, much more counterions were attracted to the surface. These ions formed a denser accumulating layer which located much nearer to the surface and caused charge inversion. The ions in this layer were non-hydrated or partially hydrated. When a voltage was applied across the nanochannel, this dense accumulating layer did not move unlike the ions near uniformly charged surface. From the water density profiles obtained in nanochannels with different surface charge distributions, the influence of the surface charge discreteness on the water distributions could be neglected.