Atomic Simulation of the Coalescence and Melting Process of Ag309 and Cu309 Clusters.

The coalescence of Cu309 and Ag309 clusters and the subsequent thermal evolution of the resulting Cu-Ag alloy clusters are systematically investigated via molecular dynamics simulations. The effects of initial coalescence distance and contact orientation on the potential energy, free energy, shape factor, and atomic packing structures are examined in detail. The results demonstrate that the activation energy for coalescence is influenced by both initial coalescence distance and the contact orientation, with the facet-to-facet orientation generally exhibiting the highest energy barrier. During the initial coalescence stage, the free energy remains essentially constant until the clusters come into contact, after which distinct evolutionary pathways emerge depending on the orientation. Upon heating, the average potential energy reveals multiple stages of atomic rearrangement, structural transition, and melting, with the transition temperatures varying significantly with the initial conditions. Shape factor analysis indicates that most clusters evolve toward a nearly spherical morphology at high temperatures, while atomic packing visualizations confirm the formation of core@partial-shell, incomplete icosahedral, and fully molten configurations depending on the temperature and initial parameters. This work provides atomic-scale insights into the coalescence behavior and thermal stability of Cu-Ag alloy clusters, offering theoretical guidance for the design and synthesis of bimetallic nanoclusters with tailored structures.