Nano-Confinement Effects on Liquid Pressure

TL;DR

This study uses molecular dynamics simulations to explore how liquid pressure in nanopores varies with pore size, revealing extreme sensitivity and the influence of solid-liquid interactions and confinement degree.

Contribution

The paper introduces a surface influence number S to quantify confinement effects and demonstrates its relationship with pore size and pressure behavior.

Findings

Pressure varies significantly with pore size, from positive to negative.

Solid-liquid interactions dominate pressure in the first liquid layer.

The S number decreases with pore size following a power law.

Abstract

In this work, molecular dynamics simulations are performed to estimate the equilibrium pressure of liquid confined in nanopores. The simulations show that the pressure is highly sensitive to the pore size and can significantly change from absolute positive to negative values for a very small (0.1 nm) change in pore size. The contribution from the solid-liquid interaction always dominates the pressure in the first liquid layer adjacent to the surface and the sensitiveness of pressure on the pore size is due to the atom distribution in the liquid layers. A surface influence number S is introduced to quantitatively characterize the degree of the confinement. The S number decreases with increasing pore size based on a power law function at constant system temperature. In nanopores with large S number, the pore liquid pressure is found to be independent of bulk liquid pressure while the pore pressure increases with bulk pressure in nanopores with small S number.