Melting of core-shell Ag-Ni and Ag-Co nanoclusters studied via molecular dynamics simulations

The melting of binary metallic nanoclusters of Ag-Ni and Ag-Co is studied at magic sizes for the anti-Mackay icosahedron by means of molecular dynamics simulations within a many-body tight-binding potential model. This structure is especially stable for those compositions at which the external shell is completely made of silver, while the inner core is either made of Ni or Co. Our simulations clearly show that melting takes place in two steps. The external one-layer thick Ag shell melts first, while the inner core is still solid, then the whole cluster melts at a temperature that can be considerably higher than the melting temperature of the external shell. The width of the temperature interval in which the shell is melted while the core is still solid strongly depends on the system.