A study using physical sphere-in-contact models to investigate the structure of close-packed nanoparticles supported on flat hexagonal, square and trigonal lattices

The tailored design of nanoparticles becomes more important with the advancement of heterogeneous catalysis and materials science. The formation of nanoparticles in catalysts with a specific geometry of the active site becomes necessary to improve activity and selectivity in catalysis. Here we have used physical sphere-in-contact models of various nanoparticles with hexagonal, square and trigonal geometries on flat close-packed surfaces to understand how the distribution of (100) and (111) sites changes as a function of nanoparticle (NP) size in a simplified model of nanoparticle supported metals. The results from this approach clearly show that in 2-layer NPs that have a hexagonal base have 2–3 times more (100) sites than the square and trigonal base NPs as a function of the number of atoms in the NP. In 3D isotropic NPs, this phenomenon is even more pronounced than the 2-layer NPs. We derive equations that estimate the number of (100), (111), the number of atoms and the aspect ratio as a function of n. These equations are important in tailoring the properties of NPs supported on close-packed metal surfaces, which may find applications in materials science, nanotechnology and catalysis.