New structural anomaly induced by nanoconfinement

TL;DR

This study uses molecular dynamics simulations to investigate how nanoconfinement and fluid-fluid interactions induce novel structural anomalies in anomalous fluids modeled by core-softened potentials.

Contribution

It reveals a new structural anomaly induced by nanoconfinement and varying attractive well depths in core-softened fluids, expanding understanding of confined anomalous fluid behavior.

Findings

A new anomalous region appears with shallow attractive wells.

Deep attractive wells lead to a single anomaly region.

Layer transitions influence the structural anomalies.

Abstract

We explore the structural properties of anomalous fluids confined in a nanopore using Molecular Dynamics simulations. The fluid is modeled by core-softened (CS) potentials that have a repulsive shoulder and an attractive well at a further distance. Changing the attractive well depth of the fluid-fluid interaction potential, we studied the behavior of the anomalies in the translational order parameter $t$ and excess entropy $s_{ex}$ for the particles near to the nanopore wall (contact layer) for systems with two or three layers of particles. When the attractive well of the CS potential is shallow, the systems present a three to two layers transition and, additionally to the usual structural anomaly, a new anomalous region in $t$ and $s_{ex}$. For attractive well deep enough, the systems change from three layers to a bulk-like profile and just one region of anomaly in $t$ and $s_{ex}$ is observed. Our results are discussed in the basis of the fluid-fluid and fluid-surface interactions.