(71f) Atomic Structure and Stress Release Mechanism of Core-Shell Au-Pd Nanocubes

The internal structure of core-shell nanoparticles has remained difficult to investigate by imaging and diffraction techniques. We report large scale molecular dynamics (MD) simulations with reliable interatomic potentials to analyze the structure of an Au-Pd core-shell nanocube of 73 nm size in all-atom resolution. The cube was prepared by random atom deposition of Pd atoms onto an Au core, similar as in solution synthesis, which allows the shell to grow epitaxially onto the core. The final equilibrium structure was studied to analyze the internal structure, lattice strain, and stress release mechanism. The stress caused by the 4.8% lattice mismatch between Au and Pd results in stacking faults at the corners of the particle and long-range arcs along the faces and edges of the particle. The results of the simulation reveal three-dimensional strain on the nanoparticles in atomic detail that has not been previously analyzed and helps explain unique properties of core-shell nanoparticles. The currently feasible resolution by coherent diffractive imaging is 6.1 nm, which has been applied to this nanoparticle and is consistent with the data presented.