Nanoparticle Confinement in Anomalous Liquids

TL;DR

This study uses molecular dynamics to explore how nanoparticle confinement affects water-like anomalies and phase transitions in liquids, revealing that ordered confinement preserves anomalies while disordered confinement suppresses them.

Contribution

It demonstrates how the structure of nanoparticle confinement influences anomalies and phase behavior in anomalous liquids, highlighting the importance of confinement order.

Findings

Ordered nanoparticle matrices preserve anomalies and shift LLPT to different conditions.

Disordered matrices suppress anomalies and restrict LLPT to a narrower density range.

Confinement increases local density heterogeneity, affecting phase behavior.

Abstract

We investigate using molecular dynamics the effect of the structure of nanoconfinement for liquids with water-like anomalies and liquid-liquid phase transition (LLPT). We find that if the confinement is in an ordered matrix of nanoparticles (NPs) the anomalies are preserved, although the LLPT shifts to lower temperatures, higher pressures and higher densities with respect to bulk. On the contrary, if the NPs matrix is disordered, we find a drastically different phase diagram: the LLPT occurs only in a reduced interval of densities and the anomalies are washed out. To understand this effect we calculate the changes in the system at the microscopic level. In all the different confinements considered here we observe a dramatic increase of density of liquid near the confining NPs. In the disordered case the confinement induces larger heterogeneity in the local density, responsible for the weakening of the LLPT and the disappearance of anomalies.