Selected properties of a 2869-atom Ni_core@Ag_shell nanoparticlewith 28% silver, initially consisting of two pure nickel and silver nanoparticles in contact with each other, evolving at 500 K or 1000 K over 500 ns: gyration radius (upper panel) and mixing index (lower panel). The common initial structure, as well as the final structures at these two temperatures are shown as insets in the upper and lower panels, respectively, while the dashed lines emphasize the nearly linear time variations in the mixing index.