Insights into the surface tension and superficial density peak of molten metals from molecular dynamics

Abstract

The surface tension of molten metals plays a key role in applications such as microfluidics, welding, and additive manufacturing. These are areas where there is an increasing emphasis on micro- and nano-scale systems, for which universal and scaling relationships are needed. We report a molecular dynamics-based analysis of the size-dependence of surface tension of molten metal droplets at the nanoscale, employing the Young-Laplace law. The superficial density peak in the surface transition layer is found to persist to the nanoscale. A novel curvature radius (Rs*) based on the position of the superficial density peak is introduced to capture the effective surface of tension. This effective radius Rs* is found to reflect accurately the intrinsic surface curvature of the droplet and thereby enable an accurate and predictive universal scaling formula for the behavior of specific surface tension at the nanoscale. These results shed new light on the surface behavior of liquid metals and provide a scaling formula that can be used for further experimental and theoretical analysis.