Diffusion Enhancement in Core-softened fluid confined in nanotubes

TL;DR

This study investigates how confinement in nanotubes affects the diffusion of a core-softened fluid modeled with a two-length-scale potential, revealing diffusion enhancement in narrow channels similar to water.

Contribution

It demonstrates that confinement can enhance diffusion in core-softened fluids, providing insights into anomalous water behavior using molecular dynamics simulations.

Findings

Diffusion coefficient increases with nanotube radius in wide channels.

In narrow channels, diffusion is enhanced as the nanotube radius decreases.

The behavior is explained through the two-length-scale potential framework.

Abstract

We study the effect of confinement in the dynamical behavior of a core-softened fluid. The fluid is modeled as a two length scales potential. This potential in the bulk reproduces the anomalous behavior observed in the density and in the diffusion of liquid water. A series of $NpT$ Molecular Dynamics simulations for this two length scales fluid confined in a nanotube were performed. We obtain that the diffusion coefficient increases with the increase of the nanotube radius for wide channels as expected for normal fluids. However, for narrow channels, the confinement shows an enhancement in the diffusion coefficient when the nanotube radius decreases. This behavior, observed for water, is explained in the framework of the two length scales potential.