Local structure of Liquid-Vapour Interfaces

TL;DR

This study investigates how liquid-vapour interfaces influence the local atomic structure of liquids, revealing temperature-dependent effects such as density reduction, layering, and orientational ordering of atomic clusters.

Contribution

It introduces a structural analysis based on ground state clusters to understand interfacial effects on liquid structure across different temperatures.

Findings

High-temperature interfaces reduce local density and cluster populations.

Low-temperature interfaces exhibit pronounced layering and orientational order.

Five-fold symmetric structures are suppressed near the interface.

Abstract

The structure of a simple liquid may be characterised in terms of ground state clusters of small numbers of atoms of that same liquid. Here we use this sensitive structural probe to consider the effect of a liquid-vapour interface upon the liquid structure. At higher temperatures (above around half the critical temperature) we find that the predominant effect of the interface is to reduce the local density, which significantly suppresses the local cluster populations. At lower temperatures, however, pronounced interfacial layering is found. This appears to be connected with significant orientational ordering of clusters based on 3- and 5-membered rings, with the rings aligning perpendicular and parallel to the interface respectively. At all temperatures, we find that the population of five-fold symmetric structures is suppressed, rather than enhanced, close to the interface.