Pairing Interactions and Gibbs Adsorption at the Liquid Bi-In Surface: A Resonant X-Ray Reflectivity Study

TL;DR

This study uses resonant x-ray reflectivity to investigate surface composition and interactions in a liquid Bi-In alloy, revealing modest Bi surface enrichment contrary to typical segregation behavior, highlighting the role of attractive interactions.

Contribution

It demonstrates the first use of resonant x-ray scattering to quantify compositional changes at a liquid alloy surface, revealing unique adsorption behavior.

Findings

Modest Bi surface enrichment with 35 atomic % Bi in the first layer

Contrasts with typical complete monolayer segregation in liquid alloys

Surface adsorption dominated by attractive Bi-In interactions

Abstract

Resonant x-ray reflectivity measurements from the surface of liquid Bi22In78 find only a modest surface Bi enhancement, with 35 atomic % Bi in the first atomic layer. This is in contrast to the Gibbs adsorption in all liquid alloys studied to date, which show surface segregation of a complete monolayer of the low surface tension component. This suggests that surface adsorption in Bi-In is dominated by attractive interactions that increase the number of Bi-In neighbors at the surface. These are the first measurements in which resonant x-ray scattering has been used to quantify compositional changes induced at a liquid alloy surface.