Enhanced wavelength-dependent surface tension of liquid-vapour interfaces

TL;DR

This paper investigates the wavelength-dependent surface tension of liquid-vapor interfaces using simulations and theory, revealing a maximum at short wavelengths and implications for scattering experiments.

Contribution

It introduces a new analysis combining simulation data with an unambiguous definition of wavenumber-dependent surface tension based on correlation functions.

Findings

$\gamma(q)$ develops a maximum at short wavelengths with increasing temperature

Comparison with density functional theory supports the simulation results

Implications for interpreting GISAXS measurements at liquid interfaces

Abstract

Due to the simultaneous presence of bulk-like and interfacial fluctuations the understanding of the structure of liquid-vapour interfaces poses a long-lasting and ongoing challenge for experiments, theory, and simulations. We provide a new analysis of this topic by combining high-quality simulation data for Lennard-Jones fluids with an unambiguous definition of the wavenumber-dependent surface tension $\gamma(q)$ based on the two-point correlation function of the fluid. Upon raising the temperature, $\gamma(q)$ develops a maximum at short wavelengths. We compare these results with predictions from density functional theory. Our analysis has repercussions for the interpretation of grazing-incidence small-angle X-ray scattering (GISAXS) at liquid interfaces.