A molecular dynamics study: Structures and thermal stability of PdmPt(13-m)Ag42 ternary nanoalloys

摘要

Structural optimization of ternary PdmPt(13-m)Ag42 nanoalloys was performed using the basin-hopping algorithm, and the Gupta many-body potential was adopted to model interatomic interaction. The optimization results show that all compositions have a structure based on icosahedron with a coreshell segregation. While the Ag atoms prefer to segregate to the surface, Pd and Pt atoms were located at the core of the cluster due to the higher surface and cohesive energy. The single platinum atom with the highest cohesive energy in Pd12Pt1Ag42 nanoalloy was located at the center of the cluster. Also in all other compositions except Pd13Ag42, Pd atoms occupy the second shell position of the icosahedron structure. We used classical molecular dynamics (MD) simulations in canonical ensemble conditions (NVT) to investigate the melting temperatures of ternary PdmPt(13-m)Ag42 nanoalloys with the interatomic interactions modeled by the same potential with optimizations. The icosahedral structures were taken as the initial configurations for MD simulations. We obtained caloric curves and Lindemann indexes to investigate the melting transitions. The simulation results showed that varying the composition gives rise to a fluctuation in melting temperatures. The highest melting temperature belongs to the Pd9Pt4Ag42 nanoalloy cluster within the other compositions. However, the relative stability investigation indicates the Pd8Pt5Ag42 nanoalloy cluster as the most stable composition. The Lindemann indexes obtained for the second and third shell of icosahedral structures show that the melting takes place as a whole without any surface premelting.