Simple prediction of immiscible metal alloying based on metastability analysis

TL;DR

This paper presents a simple energetic analysis method to predict surface alloying of immiscible metals, successfully explaining experimental observations and predicting new stable alloy formations on metal surfaces.

Contribution

It introduces a metastability analysis approach to predict surface alloying of immiscible metals, highlighting the role of B2-type structures in stability.

Findings

B2-type structures become stable for XZ and YZ alloys on surfaces.

The method explains experimental Pb-Sn alloy formation on Rh and Ru surfaces.

Predictions include new metal substrate combinations for alloy formation.

Abstract

It has been known that even though two elemental metals, $X$ and $Y$, are immiscible, they can form alloys on surfaces of other metal $Z$. In order to understand such surface alloying of immiscible metals, we study the energetic stability of binary alloys, $XZ$ and $YZ$, in several structures with various coordination numbers (CNs). By analyzing the formation energy modified to enhance the subtle energy difference between metastable structures, we find that $XZ$ and $YZ$ with B2-type structure (CN$=$8) become energetically stable when the $X$ and $Y$ metals form an alloy on the $Z$ metal surface. This is consistent with the experimental results for Pb-Sn alloys on metal surfaces such as Rh(111) and Ru(0001). Some suitable metal substrates are also predicted to form Pb-Sn alloys.