Dynamic surface tension of the pure liquid-vapor interface subjected to the cyclic loads

TL;DR

This study investigates how a pure liquid-vapor interface, specifically molten lead, responds to cyclic mechanical loads, revealing oscillation behaviors and dynamic surface tension changes that align with classical physics under high-frequency excitations.

Contribution

It introduces a computational methodology to analyze the dynamic surface tension response of liquid surfaces under cyclic loads, connecting atomic-scale correlations with macroscopic oscillation phenomena.

Findings

Dynamic surface tension oscillates under cyclic loads.

High-frequency excitation causes up to 5% increase in mean surface tension.

Instantaneous surface tension varies by up to 40% from equilibrium.

Abstract

We demonstrate a methodology for computationally investigating the mechanical response of a pure molten lead surface system to the lateral mechanical cyclic loads and try to answer the question: how dose the dynamically driven liquid surface system follow the classical physics of the elastic-driven oscillation? The steady-state oscillation of the dynamic surface tension under cyclic load, including the excitation of high frequency vibration mode at different driving frequencies and amplitudes, was compared with the classical theory of single-body driven damped oscillator. Under the highest studied frequency (50 GHz) and amplitude (5%) of the load, the increase of the (mean value) dynamic surface tension could reach ~5%. The peak and trough values of the instantaneous dynamic surface tension could reach (up to) 40% increase and (up to) 20% decrease compared to the equilibrium surface tension, respectively. The extracted generalized natural frequencies and the generalized damping constants seem to be intimately related to the intrinsic timescales of the atomic temporal-spatial correlation functions of the liquids both in the bulk region and in the outermost surface layers. These insights uncovered could be helpful for quantitative manipulation of the liquid surface tension using ultrafast shockwaves or laser pulses.