Energetics of the formation of Cu-Ag core-shell nanoparticles

This work presents molecular dynamics and Monte Carlo simulations aimed at developing an understanding of the formation of core-shell Cu-Ag nanoparticles. The effects of surface and interfacial energies were considered and used to form a phenomenological model that calculates the energy gained upon the formation of a core-shell structure from two previously distinct, non-interacting nanoparticles. In the majority of cases, the core-shell structure was found to be energetically favored. Specifically, the difference in energy as a function of the radii of the individual Cu and Ag particles was examined, with the assumption that a core-shell structure forms. In general, it was found that the energetic gain from forming such a structure increased with increasing size of the initial Ag particle. This result was interpreted as a result of the reduction in surface energy. For two separate particles, both Cu and Ag contribute to the surface energy; however, for a core-shell structure, the only contribution to the surface energy is from the Ag shell and the Cu contribution is changed to a Cu-Ag interfacial energy, which is always smaller.