Can Ordered Precursors Promote the Nucleation of Solid Solutions?

TL;DR

This study uses molecular simulation to reveal a new nucleation pathway for copper-gold solid solutions involving a chemically ordered precursor, highlighting the role of ordered intermediates in promoting nucleation.

Contribution

It uncovers a novel nucleation mechanism involving liquid and ordered precursor stages, emphasizing the importance of ordered intermediates in solid solution formation.

Findings

Identification of a liquid→L1_2 precursor→solid solution pathway

Low formation energy of L1_2 clusters promotes nucleation

Mechanism is composition-dependent due to energy differences of phases

Abstract

Crystallization often proceeds through successive stages that lead to a gradual increase in organization. Using molecular simulation, we determine the nucleation pathway for solid solutions of copper and gold. We identify a new nucleation mechanism (liquid$\to$$L1_2$~precursor$\to$solid solution), involving a chemically ordered intermediate that is more organized than the end product. This nucleation pathway arises from the low formation energy of $L1_2$ clusters which, in turn, promote crystal nucleation. We also show that this mechanism is composition-dependent since the high formation energy of other ordered phases precludes them from acting as precursors.