Dumbbell-like, core-shell and Janus-like configurations in Pd@Au@Pd three-shell nanoalloys: a molecular dynamics study

In this study, molecular dynamics simulation was used to investigate the effects of nanocluster size and its composition on the thermodynamic stability and structural evolutions of icosahedral Pd@Au@Pd three-shell nanoalloys. It was concluded that the thermal stability of Pd@Au@Pd nanoalloys is significantly dependent on their size and composition in such a way that the increase of nanoparticle size and the decrease of its Au concentration leads to the increase of its melting point. Also, the total mechanism of melting does not depend on nanoparticle size and its composition. The melting process starts from the surface of the nanocluster and leads to the segregation of Au atoms on the surface and the aggregation of Pd atoms in the core region. The final stable structure after the melting point is dependent on the nanoparticle size. For small nanoclusters, a Janus-like structure is formed after the melting point. However, for larger nanoclusters there is a competition between Janus-like and core-shell structures and after the creation of an unstable dumbbell-like intermediate structure, a stable Pd@Au core-shell structure is obtained after the melting point.