In this study, we investigated the mechanical behavior of pristine copper (Cu) nanoparticles (NPs) and Cu@graphene (Cu@G) hybrid NPs using molecular dynamics simulations.

In this work we investigate the mechanical response of Pd nanocubes and Au@Pd core-shell nanoparticles subjected to compression by an external indenter. In pristine Pd nanocubes, stacking faults across de whole cube was observed by means of transmission electron microscopy during plastic deformations. In contrast, for the Au@Pd core-shell nanocubes, such structural failures were blocked by the Au core. After a few indenter cycles, strain hardening was obtained. The same mechanical response and the hardening effect were both observed in our Molecular Dynamics simulations, which allowed us to understand the mechanisms involved with atomistic detail: For Au@Pd core-shell nanocubes, our simulations show nucleation of Shockley partial dislocations starting at the core-shell interface. After emission, they disappear at the cube outer surface, leaving behind stacking faults. It was found, however, that as strain increases a more complex dislocation structure is observed. According to the simulations, strain hardening is a consequence of dislocation junctions that take place after repeated indentations. Finally, the simulations revealed that increasing the gold core size decreases the maximum load of the nanocubes. Our work clearly shows that mechanical properties of nanoparticles can be improved significantly by combining two or more metals using core shell structures.

The thermal stability of bimetallic nanoparticles plays a crucial role in their performance in applications in catalysis, biotechnology, and materials science. In this study, we employ molecular dynamics simulations to investigate the melting behavior of Au-Pd nanoparticles with cuboctahedral, icosahedral, and decahedral geometries. Using a tight-binding potential, we systematically explore the effects of particle size and composition on the melting transition. Our analysis, based on caloric curves, Lindemann coefficients, and orientational order parameters, reveals distinct premelting behaviors influenced by geometry. Larger particles exhibit a coexistence of a pseudo-crystalline core and a partially melted shell, but, in decahedra and icosahedra, melting of the core occurs unevenly, with twin boundaries promoting the melting of one or two of the tetrahedral subunits before the rest of the particle. Notably, icosahedral nanoparticles display higher thermal stability, while both icosahedral and decahedral structures exhibit localized melting within twin boundaries. Additionally, we generate HAADF-STEM simulations to aid the interpretation of in situ electron microscopy experiments.