Stability of Pd@void@M (M=Ni, Ag, and Pt) yolk shell nanoparticles controlled by structural factors: A molecular dynamics perspective

Abstract

In this study, thermodynamic stabilities of Pd@void@M (M = Ag, Pt, Ni) yolk-shell nanoparticles are investigated at room temperature by molecular dynamics simulation. The effects of various structural parameters such as shell thickness, geometries of the shell and the core, core size, and alloying of Pd with the shell atoms on the stability of these materials are considered. For this aim, various parameters have been applied such as surface energy, excess energy, and strain. The results indicate that all of the simulated nanoparticles are instable at room temperature and association of the core expansion and the shell contraction leads to creation of core-shell nanoparticles with higher thermodynamic stability. Moreover, the simulations demonstrate that for these nanoparticles, the effect of surface energy is dominant in such a way that Pd@void@Ag nanoparticle with the lowest surface energy and Pd@void@Pt nanoparticle with the highest surface energy exhibit the highest and the lowest stabilities, respectively. In addition, for these nanostructures with different geometries of the core and the shell and also, for different core sizes, surface energy and strain play role on the stabilities of them without any competition. Whereas for the structures with different shell thickness and Pd concentration in the shell region, strain and surface energy acts as dominant factors in thermodynamic stabilities of these nanostructures, respectively. Generally, the results of simulations indicate that by controlling of the structural factors one can increase the stability of yolk-shell nanoparticles in order to synthesize the more stable structures of them.