Reshaping of Truncated Pd Nanocubes: Atomistic Modeling and TEM analysis

Stability against reshaping of metallic fcc nanocrystals synthesized with tailored far-from-equilibrium shapes is key to maintaining optimal properties for applications such as catalysis and plasmonics. We develop a stochastic atomistic model and perform KMC simulations for reshaping mediated by surface diffusion incorporating realistic diffusion kinetics across and between different facets, along step edges and around corners, etc. For the reshaping of fcc metal nanocubes, we also provide an analytic determination of the energy variation along the optimal pathway for reshaping which involves transfer of atoms across the nanocube surface from edges or corners to form new layers on side {100} facets. The effective barrier from this analysis is shown to increase strongly with the degree of truncation of edges and corners in the synthesized nanocube. Theory matches and elucidates experimental TEM results for the reshaping kinetics for Pd nanocubes yielding a high effective barrier of E_eff » 4.6 eV for the appropriate degree of truncation. Reference: ACS Nano 14 (2020) 8551.