Anomaly of the dielectric function of water under confinement and its role in Van der Waals interactions

TL;DR

This paper theoretically investigates how water's dielectric properties change under confinement and how this affects Van der Waals forces, revealing significant reductions in the Hamaker constant with dielectric walls but not metallic ones.

Contribution

It provides a theoretical analysis of the dielectric function reduction of water under confinement and its impact on Van der Waals interactions, including effects with electrolytes.

Findings

Dielectric function of water drops from 79 to 2 under confinement.

Hamaker constant decreases by nearly 90% with dielectric walls.

Confinement can reduce Debye screening length without changing salt concentration.

Abstract

We present a theoretical calculation of the changes in the Hamaker constant due to the anomalous reduction of the static dielectric function of water. Under confinement, the dielectric function of water decreases from a bulk value of 79 down to 2. If the confining walls are made of a dielectric material, the Hamaker constant reduces almost by 90\%. However, if the confinement is realized with metallic plates, there is little change in the Hamaker constant. Additionally, we show that confinement can be used to decreases the Debye screening length without changing the salt concentration. This, in turn, is used to change the Hamaker constant in the presence of electrolytes.